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	$175.28	12.184%	$196.6361	$196.64	$196.65	$196.60
Purchase #2	$153.72	7.672%	$165.5134	$165.51	$165.50	$165.50
Purchase #3	$190.51	12.623%	$214.5581	$214.56	$214.55	$214.60
Purchase #4	$210.74	12.189%	$236.4271	$236.43	$236.45	$236.40
Purchase #5	$25.86	10.381%	$28.5445	$28.54	$28.55	$28.50
Purchase #6	$84.78	5.206%	$89.1936	$89.19	$89.20	$89.20
Purchase #7	$214.42	5.607%	$226.4425	$226.44	$226.45	$226.40
7 purchase totals =	$1,055.31		$1,157.3153	$1,157.31	$1,157.35	$1,157.20