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	$200.76	4.456%	$209.7059	$209.71	$209.70	$209.70
Purchase #2	$108.91	13.307%	$123.4027	$123.40	$123.40	$123.40
Purchase #3	$96.57	3.609%	$100.0552	$100.06	$100.05	$100.10
Purchase #4	$220.27	10.251%	$242.8499	$242.85	$242.85	$242.80
Purchase #5	$154.72	4.732%	$162.0414	$162.04	$162.05	$162.00
Purchase #6	$158.90	6.531%	$169.2778	$169.28	$169.30	$169.30
Purchase #7	$90.49	10.720%	$100.1905	$100.19	$100.20	$100.20
7 purchase totals =	$1,030.62		$1,107.5234	$1,107.53	$1,107.55	$1,107.50