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	$64.42	4.335%	$67.2126	$67.21	$67.20	$67.20
Purchase #2	$151.86	13.369%	$172.1622	$172.16	$172.15	$172.20
Purchase #3	$57.90	7.858%	$62.4498	$62.45	$62.45	$62.40
Purchase #4	$201.83	13.473%	$229.0226	$229.02	$229.00	$229.00
Purchase #5	$133.52	5.446%	$140.7915	$140.79	$140.80	$140.80
Purchase #6	$47.83	6.597%	$50.9853	$50.99	$51.00	$51.00
Purchase #7	$199.36	11.300%	$221.8877	$221.89	$221.90	$221.90
7 purchase totals =	$856.72		$944.5117	$944.51	$944.50	$944.50