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	$20.94	9.213%	$22.8692	$22.87	$22.85	$22.90
Purchase #2	$107.31	3.555%	$111.1249	$111.12	$111.10	$111.10
Purchase #3	$248.48	11.704%	$277.5621	$277.56	$277.55	$277.60
Purchase #4	$229.88	5.482%	$242.482	$242.48	$242.50	$242.50
Purchase #5	$80.40	10.872%	$89.1411	$89.14	$89.15	$89.10
Purchase #6	$155.27	8.652%	$168.704	$168.70	$168.70	$168.70
Purchase #7	$196.39	8.376%	$212.8396	$212.84	$212.85	$212.80
7 purchase totals =	$1,038.67		$1,124.7229	$1,124.71	$1,124.70	$1,124.70