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	$74.38	3.369%	$76.8859	$76.89	$76.90	$76.90
Purchase #2	$62.99	13.109%	$71.2474	$71.25	$71.25	$71.20
Purchase #3	$236.90	7.801%	$255.3806	$255.38	$255.40	$255.40
Purchase #4	$202.35	13.151%	$228.961	$228.96	$228.95	$229.00
Purchase #5	$41.66	4.498%	$43.5339	$43.53	$43.55	$43.50
Purchase #6	$34.39	5.212%	$36.1824	$36.18	$36.20	$36.20
Purchase #7	$225.88	11.184%	$251.1424	$251.14	$251.15	$251.10
7 purchase totals =	$878.55		$963.3336	$963.33	$963.40	$963.30