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	$24.29	8.768%	$26.4197	$26.42	$26.40	$26.40
Purchase #2	$16.93	11.551%	$18.8856	$18.89	$18.90	$18.90
Purchase #3	$230.52	12.399%	$259.1022	$259.10	$259.10	$259.10
Purchase #4	$112.96	10.438%	$124.7508	$124.75	$124.75	$124.80
Purchase #5	$209.30	6.481%	$222.8647	$222.86	$222.85	$222.90
Purchase #6	$173.97	12.790%	$196.2208	$196.22	$196.20	$196.20
Purchase #7	$152.46	5.421%	$160.7249	$160.72	$160.70	$160.70
7 purchase totals =	$920.43		$1,008.9687	$1,008.96	$1,008.90	$1,009.00