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	$119.92	11.358%	$133.5405	$133.54	$133.55	$133.50
Purchase #2	$152.76	7.690%	$164.5072	$164.51	$164.50	$164.50
Purchase #3	$229.71	11.162%	$255.3502	$255.35	$255.35	$255.40
Purchase #4	$220.29	6.122%	$233.7762	$233.78	$233.80	$233.80
Purchase #5	$55.41	12.804%	$62.5047	$62.50	$62.50	$62.50
Purchase #6	$116.48	7.521%	$125.2405	$125.24	$125.25	$125.20
Purchase #7	$65.26	3.730%	$67.6942	$67.69	$67.70	$67.70
7 purchase totals =	$959.83		$1,042.6135	$1,042.61	$1,042.65	$1,042.60