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	$141.31	3.606%	$146.4056	$146.41	$146.40	$146.40
Purchase #2	$168.74	9.248%	$184.3451	$184.35	$184.35	$184.30
Purchase #3	$173.35	6.298%	$184.2676	$184.27	$184.25	$184.30
Purchase #4	$157.71	7.647%	$169.7701	$169.77	$169.75	$169.80
Purchase #5	$248.95	9.231%	$271.9306	$271.93	$271.95	$271.90
Purchase #6	$38.30	5.551%	$40.426	$40.43	$40.45	$40.40
Purchase #7	$169.38	12.502%	$190.5559	$190.56	$190.55	$190.60
7 purchase totals =	$1,097.74		$1,187.7009	$1,187.72	$1,187.70	$1,187.70