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	$214.87	7.817%	$231.6664	$231.67	$231.65	$231.70
Purchase #2	$214.82	13.369%	$243.5393	$243.54	$243.55	$243.50
Purchase #3	$118.91	7.573%	$127.9151	$127.92	$127.90	$127.90
Purchase #4	$125.92	6.847%	$134.5417	$134.54	$134.55	$134.50
Purchase #5	$91.74	9.801%	$100.7314	$100.73	$100.75	$100.70
Purchase #6	$238.79	9.490%	$261.4512	$261.45	$261.45	$261.50
Purchase #7	$84.41	5.780%	$89.2889	$89.29	$89.30	$89.30
7 purchase totals =	$1,089.46		$1,189.1340	$1,189.14	$1,189.15	$1,189.10