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	$197.35	12.632%	$222.2793	$222.28	$222.30	$222.30
Purchase #2	$233.47	7.144%	$250.1491	$250.15	$250.15	$250.10
Purchase #3	$48.64	4.212%	$50.6887	$50.69	$50.70	$50.70
Purchase #4	$99.67	11.214%	$110.847	$110.85	$110.85	$110.80
Purchase #5	$32.41	8.506%	$35.1668	$35.17	$35.15	$35.20
Purchase #6	$136.84	6.589%	$145.8564	$145.86	$145.85	$145.90
Purchase #7	$177.50	10.581%	$196.2813	$196.28	$196.30	$196.30
7 purchase totals =	$925.88		$1,011.2686	$1,011.28	$1,011.30	$1,011.30