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	$221.58	13.129%	$250.6712	$250.67	$250.65	$250.70
Purchase #2	$131.88	12.330%	$148.1408	$148.14	$148.15	$148.10
Purchase #3	$119.40	11.792%	$133.4796	$133.48	$133.50	$133.50
Purchase #4	$200.94	4.278%	$209.5362	$209.54	$209.55	$209.50
Purchase #5	$56.73	13.693%	$64.498	$64.50	$64.50	$64.50
Purchase #6	$202.74	10.419%	$223.8635	$223.86	$223.85	$223.90
Purchase #7	$18.38	4.747%	$19.2525	$19.25	$19.25	$19.30
7 purchase totals =	$951.65		$1,049.4418	$1,049.44	$1,049.45	$1,049.50