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	$66.75	8.562%	$72.4651	$72.47	$72.45	$72.50
Purchase #2	$229.52	13.525%	$260.5626	$260.56	$260.55	$260.60
Purchase #3	$120.95	11.448%	$134.7964	$134.80	$134.80	$134.80
Purchase #4	$230.32	6.831%	$246.0532	$246.05	$246.05	$246.10
Purchase #5	$233.30	9.693%	$255.9138	$255.91	$255.90	$255.90
Purchase #6	$182.95	7.386%	$196.4627	$196.46	$196.45	$196.50
Purchase #7	$225.83	8.197%	$244.3413	$244.34	$244.35	$244.30
7 purchase totals =	$1,289.62		$1,410.5951	$1,410.59	$1,410.55	$1,410.70