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	$155.65	7.375%	$167.1292	$167.13	$167.15	$167.10
Purchase #2	$133.33	4.670%	$139.5565	$139.56	$139.55	$139.60
Purchase #3	$52.39	11.708%	$58.5238	$58.52	$58.50	$58.50
Purchase #4	$210.88	6.491%	$224.5682	$224.57	$224.55	$224.60
Purchase #5	$161.37	4.365%	$168.4138	$168.41	$168.40	$168.40
Purchase #6	$55.54	6.292%	$59.0346	$59.03	$59.05	$59.00
Purchase #7	$225.67	9.667%	$247.4855	$247.49	$247.50	$247.50
7 purchase totals =	$994.83		$1,064.7116	$1,064.71	$1,064.70	$1,064.70