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	$184.54	13.553%	$209.5507	$209.55	$209.55	$209.60
Purchase #2	$142.75	6.123%	$151.4906	$151.49	$151.50	$151.50
Purchase #3	$75.44	8.751%	$82.0418	$82.04	$82.05	$82.00
Purchase #4	$74.95	13.255%	$84.8846	$84.88	$84.90	$84.90
Purchase #5	$104.78	6.259%	$111.3382	$111.34	$111.35	$111.30
Purchase #6	$93.64	6.182%	$99.4288	$99.43	$99.45	$99.40
Purchase #7	$185.51	3.151%	$191.3554	$191.36	$191.35	$191.40
7 purchase totals =	$861.61		$930.0901	$930.09	$930.15	$930.10