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	$174.39	9.173%	$190.3868	$190.39	$190.40	$190.40
Purchase #2	$54.95	11.499%	$61.2687	$61.27	$61.25	$61.30
Purchase #3	$157.57	12.465%	$177.2111	$177.21	$177.20	$177.20
Purchase #4	$56.41	5.304%	$59.402	$59.40	$59.40	$59.40
Purchase #5	$165.65	11.145%	$184.1117	$184.11	$184.10	$184.10
Purchase #6	$236.83	8.461%	$256.8682	$256.87	$256.85	$256.90
Purchase #7	$65.93	6.849%	$70.4455	$70.45	$70.45	$70.40
7 purchase totals =	$911.73		$999.6940	$999.70	$999.65	$999.70