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	$141.72	4.339%	$147.8692	$147.87	$147.85	$147.90
Purchase #2	$197.73	4.648%	$206.9205	$206.92	$206.90	$206.90
Purchase #3	$90.37	10.342%	$99.7161	$99.72	$99.70	$99.70
Purchase #4	$100.40	13.782%	$114.2371	$114.24	$114.25	$114.20
Purchase #5	$237.31	3.776%	$246.2708	$246.27	$246.25	$246.30
Purchase #6	$177.91	6.639%	$189.7214	$189.72	$189.70	$189.70
Purchase #7	$208.72	7.121%	$223.583	$223.58	$223.60	$223.60
7 purchase totals =	$1,154.16		$1,228.3181	$1,228.32	$1,228.25	$1,228.30