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	$99.31	4.490%	$103.769	$103.77	$103.75	$103.80
Purchase #2	$81.89	13.497%	$92.9427	$92.94	$92.95	$92.90
Purchase #3	$222.43	11.581%	$248.1896	$248.19	$248.20	$248.20
Purchase #4	$179.47	7.629%	$193.1618	$193.16	$193.15	$193.20
Purchase #5	$227.57	12.763%	$256.6148	$256.61	$256.60	$256.60
Purchase #6	$101.80	4.445%	$106.325	$106.33	$106.35	$106.30
Purchase #7	$105.31	6.232%	$111.8729	$111.87	$111.85	$111.90
7 purchase totals =	$1,017.78		$1,112.8758	$1,112.87	$1,112.85	$1,112.90