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	$171.71	11.255%	$191.036	$191.04	$191.05	$191.00
Purchase #2	$43.86	9.324%	$47.9495	$47.95	$47.95	$47.90
Purchase #3	$69.36	3.212%	$71.5878	$71.59	$71.60	$71.60
Purchase #4	$73.43	6.839%	$78.4519	$78.45	$78.45	$78.50
Purchase #5	$83.43	9.514%	$91.3675	$91.37	$91.35	$91.40
Purchase #6	$96.37	4.744%	$100.9418	$100.94	$100.95	$100.90
Purchase #7	$57.53	12.760%	$64.8708	$64.87	$64.85	$64.90
7 purchase totals =	$595.69		$646.2053	$646.21	$646.20	$646.20