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	$67.59	6.149%	$71.7461	$71.75	$71.75	$71.70
Purchase #2	$20.81	11.701%	$23.245	$23.25	$23.25	$23.20
Purchase #3	$115.59	10.872%	$128.1569	$128.16	$128.15	$128.20
Purchase #4	$167.27	5.298%	$176.132	$176.13	$176.15	$176.10
Purchase #5	$62.53	3.606%	$64.7848	$64.78	$64.80	$64.80
Purchase #6	$77.28	10.634%	$85.498	$85.50	$85.50	$85.50
Purchase #7	$42.27	6.328%	$44.9448	$44.94	$44.95	$44.90
7 purchase totals =	$553.34		$594.5076	$594.51	$594.55	$594.40