Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$135.50	7.653%	$145.8698	$145.87	$145.85	$145.90
Purchase #2	$215.30	13.359%	$244.0619	$244.06	$244.05	$244.10
Purchase #3	$158.72	4.301%	$165.5465	$165.55	$165.55	$165.50
Purchase #4	$151.62	6.540%	$161.5359	$161.54	$161.55	$161.50
Purchase #5	$163.68	13.482%	$185.7473	$185.75	$185.75	$185.70
Purchase #6	$162.54	3.528%	$168.2744	$168.27	$168.25	$168.30
Purchase #7	$223.69	8.664%	$243.0705	$243.07	$243.05	$243.10
7 purchase totals =	$1,211.05		$1,314.1063	$1,314.11	$1,314.05	$1,314.10