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	$39.38	10.401%	$43.4759	$43.48	$43.50	$43.50
Purchase #2	$183.43	7.653%	$197.4679	$197.47	$197.45	$197.50
Purchase #3	$244.92	6.618%	$261.1288	$261.13	$261.15	$261.10
Purchase #4	$32.79	8.190%	$35.4755	$35.48	$35.50	$35.50
Purchase #5	$97.32	6.610%	$103.7529	$103.75	$103.75	$103.80
Purchase #6	$135.87	4.434%	$141.8945	$141.89	$141.90	$141.90
Purchase #7	$195.32	12.488%	$219.7116	$219.71	$219.70	$219.70
7 purchase totals =	$929.03		$1,002.9071	$1,002.91	$1,002.95	$1,003.00