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	$135.89	11.188%	$151.0934	$151.09	$151.10	$151.10
Purchase #2	$97.30	13.242%	$110.1845	$110.18	$110.20	$110.20
Purchase #3	$47.26	6.629%	$50.3929	$50.39	$50.40	$50.40
Purchase #4	$204.76	4.184%	$213.3272	$213.33	$213.35	$213.30
Purchase #5	$127.81	10.799%	$141.6122	$141.61	$141.60	$141.60
Purchase #6	$245.69	13.224%	$278.18	$278.18	$278.20	$278.20
Purchase #7	$62.52	13.666%	$71.064	$71.06	$71.05	$71.10
7 purchase totals =	$921.23		$1,015.8542	$1,015.84	$1,015.90	$1,015.90