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	$201.60	5.596%	$212.8815	$212.88	$212.90	$212.90
Purchase #2	$120.80	5.332%	$127.2411	$127.24	$127.25	$127.20
Purchase #3	$146.37	9.197%	$159.8316	$159.83	$159.85	$159.80
Purchase #4	$91.43	8.354%	$99.0681	$99.07	$99.05	$99.10
Purchase #5	$47.62	6.619%	$50.772	$50.77	$50.75	$50.80
Purchase #6	$202.32	4.585%	$211.5964	$211.60	$211.60	$211.60
Purchase #7	$218.54	11.572%	$243.8294	$243.83	$243.85	$243.80
7 purchase totals =	$1,028.68		$1,105.2201	$1,105.22	$1,105.25	$1,105.20