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	$236.58	7.337%	$253.9379	$253.94	$253.95	$253.90
Purchase #2	$182.80	7.339%	$196.2157	$196.22	$196.20	$196.20
Purchase #3	$247.40	7.662%	$266.3558	$266.36	$266.35	$266.40
Purchase #4	$65.44	10.755%	$72.4781	$72.48	$72.50	$72.50
Purchase #5	$6.50	12.444%	$7.3089	$7.31	$7.30	$7.30
Purchase #6	$126.31	10.496%	$139.5675	$139.57	$139.55	$139.60
Purchase #7	$114.31	12.676%	$128.7999	$128.80	$128.80	$128.80
7 purchase totals =	$979.34		$1,064.6638	$1,064.68	$1,064.65	$1,064.70