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	$38.87	4.735%	$40.7105	$40.71	$40.70	$40.70
Purchase #2	$170.58	12.609%	$192.0884	$192.09	$192.10	$192.10
Purchase #3	$89.33	3.658%	$92.5977	$92.60	$92.60	$92.60
Purchase #4	$48.89	12.281%	$54.8942	$54.89	$54.90	$54.90
Purchase #5	$109.61	4.198%	$114.2114	$114.21	$114.20	$114.20
Purchase #6	$235.28	4.175%	$245.1029	$245.10	$245.10	$245.10
Purchase #7	$221.42	7.156%	$237.2648	$237.26	$237.25	$237.30
7 purchase totals =	$913.98		$976.8699	$976.86	$976.85	$976.90