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	$221.29	7.502%	$237.8912	$237.89	$237.90	$237.90
Purchase #2	$46.45	5.830%	$49.158	$49.16	$49.15	$49.20
Purchase #3	$116.25	10.229%	$128.1412	$128.14	$128.15	$128.10
Purchase #4	$193.83	3.368%	$200.3582	$200.36	$200.35	$200.40
Purchase #5	$158.31	13.773%	$180.114	$180.11	$180.10	$180.10
Purchase #6	$59.57	6.648%	$63.5302	$63.53	$63.55	$63.50
Purchase #7	$151.87	4.396%	$158.5462	$158.55	$158.55	$158.50
7 purchase totals =	$947.57		$1,017.7390	$1,017.74	$1,017.75	$1,017.70