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	$221.60	7.428%	$238.0604	$238.06	$238.05	$238.10
Purchase #2	$152.85	3.482%	$158.1722	$158.17	$158.15	$158.20
Purchase #3	$102.88	7.459%	$110.5538	$110.55	$110.55	$110.60
Purchase #4	$247.62	11.306%	$275.6159	$275.62	$275.60	$275.60
Purchase #5	$128.29	8.758%	$139.5256	$139.53	$139.55	$139.50
Purchase #6	$124.55	8.810%	$135.5229	$135.52	$135.50	$135.50
Purchase #7	$85.44	3.439%	$88.3783	$88.38	$88.40	$88.40
7 purchase totals =	$1,063.23		$1,145.8291	$1,145.83	$1,145.80	$1,145.90