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	$105.31	5.473%	$111.0736	$111.07	$111.05	$111.10
Purchase #2	$135.56	5.728%	$143.3249	$143.32	$143.30	$143.30
Purchase #3	$20.54	11.472%	$22.8963	$22.90	$22.90	$22.90
Purchase #4	$187.75	13.320%	$212.7583	$212.76	$212.75	$212.80
Purchase #5	$191.46	8.835%	$208.3755	$208.38	$208.40	$208.40
Purchase #6	$105.77	12.261%	$118.7385	$118.74	$118.75	$118.70
Purchase #7	$63.35	11.134%	$70.4034	$70.40	$70.40	$70.40
7 purchase totals =	$809.74		$887.5705	$887.57	$887.55	$887.60