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	$78.58	5.263%	$82.7157	$82.72	$82.70	$82.70
Purchase #2	$213.66	9.288%	$233.5047	$233.50	$233.50	$233.50
Purchase #3	$57.96	6.105%	$61.4985	$61.50	$61.50	$61.50
Purchase #4	$91.32	3.290%	$94.3244	$94.32	$94.30	$94.30
Purchase #5	$131.57	9.640%	$144.2533	$144.25	$144.25	$144.30
Purchase #6	$234.63	5.775%	$248.1799	$248.18	$248.20	$248.20
Purchase #7	$30.31	8.450%	$32.8712	$32.87	$32.85	$32.90
7 purchase totals =	$838.03		$897.3477	$897.34	$897.30	$897.40