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	$93.71	12.154%	$105.0995	$105.10	$105.10	$105.10
Purchase #2	$105.79	5.322%	$111.4201	$111.42	$111.40	$111.40
Purchase #3	$201.43	4.215%	$209.9203	$209.92	$209.90	$209.90
Purchase #4	$165.67	4.768%	$173.5691	$173.57	$173.55	$173.60
Purchase #5	$25.34	4.263%	$26.4202	$26.42	$26.40	$26.40
Purchase #6	$28.86	11.298%	$32.1206	$32.12	$32.10	$32.10
Purchase #7	$70.75	4.183%	$73.7095	$73.71	$73.70	$73.70
7 purchase totals =	$691.55		$732.2593	$732.26	$732.15	$732.20