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	$177.63	13.624%	$201.8303	$201.83	$201.85	$201.80
Purchase #2	$80.78	11.576%	$90.1311	$90.13	$90.15	$90.10
Purchase #3	$148.67	6.492%	$158.3217	$158.32	$158.30	$158.30
Purchase #4	$84.96	13.864%	$96.7389	$96.74	$96.75	$96.70
Purchase #5	$246.68	9.280%	$269.5719	$269.57	$269.55	$269.60
Purchase #6	$84.64	7.431%	$90.9296	$90.93	$90.95	$90.90
Purchase #7	$222.92	12.427%	$250.6223	$250.62	$250.60	$250.60
7 purchase totals =	$1,046.28		$1,158.1458	$1,158.14	$1,158.15	$1,158.00