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	$106.91	8.814%	$116.333	$116.33	$116.35	$116.30
Purchase #2	$88.52	3.362%	$91.496	$91.50	$91.50	$91.50
Purchase #3	$204.29	10.395%	$225.5259	$225.53	$225.55	$225.50
Purchase #4	$99.28	11.761%	$110.9563	$110.96	$110.95	$111.00
Purchase #5	$80.43	12.671%	$90.6213	$90.62	$90.60	$90.60
Purchase #6	$46.57	4.292%	$48.5688	$48.57	$48.55	$48.60
Purchase #7	$169.40	12.525%	$190.6174	$190.62	$190.60	$190.60
7 purchase totals =	$795.40		$874.1187	$874.13	$874.10	$874.10