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	$209.92	9.336%	$229.5181	$229.52	$229.50	$229.50
Purchase #2	$182.64	8.361%	$197.9105	$197.91	$197.90	$197.90
Purchase #3	$116.46	13.755%	$132.4791	$132.48	$132.50	$132.50
Purchase #4	$215.86	3.717%	$223.8835	$223.88	$223.90	$223.90
Purchase #5	$86.86	10.415%	$95.9065	$95.91	$95.90	$95.90
Purchase #6	$165.67	12.738%	$186.773	$186.77	$186.75	$186.80
Purchase #7	$89.31	13.851%	$101.6803	$101.68	$101.70	$101.70
7 purchase totals =	$1,066.72		$1,168.1510	$1,168.15	$1,168.15	$1,168.20