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	$168.26	10.155%	$185.3468	$185.35	$185.35	$185.30
Purchase #2	$203.27	13.684%	$231.0855	$231.09	$231.10	$231.10
Purchase #3	$160.96	8.267%	$174.2666	$174.27	$174.25	$174.30
Purchase #4	$142.91	10.670%	$158.1585	$158.16	$158.15	$158.20
Purchase #5	$32.28	10.109%	$35.5432	$35.54	$35.55	$35.50
Purchase #6	$86.42	4.126%	$89.9857	$89.99	$90.00	$90.00
Purchase #7	$144.95	5.488%	$152.9049	$152.90	$152.90	$152.90
7 purchase totals =	$939.05		$1,027.2912	$1,027.30	$1,027.30	$1,027.30