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	$220.72	3.231%	$227.8515	$227.85	$227.85	$227.90
Purchase #2	$53.59	11.206%	$59.5953	$59.60	$59.60	$59.60
Purchase #3	$33.26	6.755%	$35.5067	$35.51	$35.50	$35.50
Purchase #4	$179.89	4.735%	$188.4078	$188.41	$188.40	$188.40
Purchase #5	$28.67	5.240%	$30.1723	$30.17	$30.15	$30.20
Purchase #6	$13.90	11.527%	$15.5023	$15.50	$15.50	$15.50
Purchase #7	$110.62	4.105%	$115.161	$115.16	$115.15	$115.20
7 purchase totals =	$640.65		$672.1969	$672.20	$672.15	$672.30