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	$162.47	3.692%	$168.4684	$168.47	$168.45	$168.50
Purchase #2	$160.58	7.797%	$173.1004	$173.10	$173.10	$173.10
Purchase #3	$31.91	13.343%	$36.1678	$36.17	$36.15	$36.20
Purchase #4	$100.40	5.474%	$105.8959	$105.90	$105.90	$105.90
Purchase #5	$58.56	5.115%	$61.5553	$61.56	$61.55	$61.60
Purchase #6	$196.26	10.513%	$216.8928	$216.89	$216.90	$216.90
Purchase #7	$174.70	7.866%	$188.4419	$188.44	$188.45	$188.40
7 purchase totals =	$884.88		$950.5225	$950.53	$950.50	$950.60