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	$195.94	8.397%	$212.3931	$212.39	$212.40	$212.40
Purchase #2	$42.72	10.339%	$47.1368	$47.14	$47.15	$47.10
Purchase #3	$52.58	13.679%	$59.7724	$59.77	$59.75	$59.80
Purchase #4	$85.96	5.287%	$90.5047	$90.50	$90.50	$90.50
Purchase #5	$101.63	6.559%	$108.2959	$108.30	$108.30	$108.30
Purchase #6	$106.79	5.185%	$112.3271	$112.33	$112.35	$112.30
Purchase #7	$138.82	10.767%	$153.7667	$153.77	$153.75	$153.80
7 purchase totals =	$724.44		$784.1967	$784.20	$784.20	$784.20