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	$43.69	4.385%	$45.6058	$45.61	$45.60	$45.60
Purchase #2	$200.60	4.254%	$209.1335	$209.13	$209.15	$209.10
Purchase #3	$116.78	11.785%	$130.5425	$130.54	$130.55	$130.50
Purchase #4	$246.78	6.394%	$262.5591	$262.56	$262.55	$262.60
Purchase #5	$80.41	10.386%	$88.7614	$88.76	$88.75	$88.80
Purchase #6	$78.52	13.620%	$89.2144	$89.21	$89.20	$89.20
Purchase #7	$40.61	4.123%	$42.2844	$42.28	$42.30	$42.30
7 purchase totals =	$807.39		$868.1011	$868.09	$868.10	$868.10