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	$125.81	13.274%	$142.51	$142.51	$142.50	$142.50
Purchase #2	$24.91	13.311%	$28.2258	$28.23	$28.25	$28.20
Purchase #3	$114.98	8.473%	$124.7223	$124.72	$124.70	$124.70
Purchase #4	$53.81	13.565%	$61.1093	$61.11	$61.10	$61.10
Purchase #5	$93.95	7.132%	$100.6505	$100.65	$100.65	$100.70
Purchase #6	$71.88	6.428%	$76.5004	$76.50	$76.50	$76.50
Purchase #7	$185.50	7.566%	$199.5349	$199.53	$199.55	$199.50
7 purchase totals =	$670.84		$733.2532	$733.25	$733.25	$733.20