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	$149.85	8.166%	$162.0868	$162.09	$162.10	$162.10
Purchase #2	$167.42	13.684%	$190.3298	$190.33	$190.35	$190.30
Purchase #3	$209.95	11.447%	$233.983	$233.98	$234.00	$234.00
Purchase #4	$163.63	5.857%	$173.2138	$173.21	$173.20	$173.20
Purchase #5	$68.97	10.803%	$76.4208	$76.42	$76.40	$76.40
Purchase #6	$55.77	6.267%	$59.2651	$59.27	$59.25	$59.30
Purchase #7	$111.91	11.157%	$124.3958	$124.40	$124.40	$124.40
7 purchase totals =	$927.50		$1,019.6951	$1,019.70	$1,019.70	$1,019.70