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	$247.68	9.162%	$270.3724	$270.37	$270.35	$270.40
Purchase #2	$44.52	6.656%	$47.4833	$47.48	$47.50	$47.50
Purchase #3	$208.85	11.624%	$233.1267	$233.13	$233.15	$233.10
Purchase #4	$231.29	13.344%	$262.1533	$262.15	$262.15	$262.20
Purchase #5	$10.85	13.632%	$12.3291	$12.33	$12.35	$12.30
Purchase #6	$58.83	11.123%	$65.3737	$65.37	$65.35	$65.40
Purchase #7	$231.88	5.154%	$243.8311	$243.83	$243.85	$243.80
7 purchase totals =	$1,033.90		$1,134.6696	$1,134.66	$1,134.70	$1,134.70