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	$175.36	5.429%	$184.8803	$184.88	$184.90	$184.90
Purchase #2	$170.83	12.139%	$191.5671	$191.57	$191.55	$191.60
Purchase #3	$216.77	10.791%	$240.1617	$240.16	$240.15	$240.20
Purchase #4	$81.94	11.871%	$91.6671	$91.67	$91.65	$91.70
Purchase #5	$151.90	8.655%	$165.0469	$165.05	$165.05	$165.00
Purchase #6	$171.71	10.147%	$189.1334	$189.13	$189.15	$189.10
Purchase #7	$154.71	4.858%	$162.2258	$162.23	$162.25	$162.20
7 purchase totals =	$1,123.22		$1,224.6823	$1,224.69	$1,224.70	$1,224.70