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	$147.38	13.263%	$166.927	$166.93	$166.95	$166.90
Purchase #2	$125.97	13.805%	$143.3602	$143.36	$143.35	$143.40
Purchase #3	$100.63	4.725%	$105.3848	$105.38	$105.40	$105.40
Purchase #4	$108.36	10.567%	$119.8104	$119.81	$119.80	$119.80
Purchase #5	$211.58	8.282%	$229.1031	$229.10	$229.10	$229.10
Purchase #6	$123.96	7.655%	$133.4491	$133.45	$133.45	$133.40
Purchase #7	$195.43	13.667%	$222.1394	$222.14	$222.15	$222.10
7 purchase totals =	$1,013.31		$1,120.1740	$1,120.17	$1,120.20	$1,120.10