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	$223.90	10.336%	$247.0423	$247.04	$247.05	$247.00
Purchase #2	$27.60	11.608%	$30.8038	$30.80	$30.80	$30.80
Purchase #3	$166.66	10.501%	$184.161	$184.16	$184.15	$184.20
Purchase #4	$210.69	6.196%	$223.7444	$223.74	$223.75	$223.70
Purchase #5	$154.28	12.873%	$174.1405	$174.14	$174.15	$174.10
Purchase #6	$213.71	4.763%	$223.889	$223.89	$223.90	$223.90
Purchase #7	$59.56	13.692%	$67.715	$67.72	$67.70	$67.70
7 purchase totals =	$1,056.40		$1,151.4960	$1,151.49	$1,151.50	$1,151.40