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	$230.91	5.624%	$243.8964	$243.90	$243.90	$243.90
Purchase #2	$64.72	8.400%	$70.1565	$70.16	$70.15	$70.20
Purchase #3	$233.56	5.836%	$247.1906	$247.19	$247.20	$247.20
Purchase #4	$80.89	11.148%	$89.9076	$89.91	$89.90	$89.90
Purchase #5	$142.45	3.113%	$146.8845	$146.88	$146.90	$146.90
Purchase #6	$234.64	6.549%	$250.0066	$250.01	$250.00	$250.00
Purchase #7	$139.70	5.549%	$147.452	$147.45	$147.45	$147.50
7 purchase totals =	$1,126.87		$1,195.4942	$1,195.50	$1,195.50	$1,195.60