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	$58.86	5.808%	$62.2786	$62.28	$62.30	$62.30
Purchase #2	$106.79	3.480%	$110.5063	$110.51	$110.50	$110.50
Purchase #3	$90.55	6.513%	$96.4475	$96.45	$96.45	$96.40
Purchase #4	$140.51	4.213%	$146.4297	$146.43	$146.45	$146.40
Purchase #5	$98.96	13.321%	$112.1425	$112.14	$112.15	$112.10
Purchase #6	$151.42	4.648%	$158.458	$158.46	$158.45	$158.50
Purchase #7	$146.52	3.436%	$151.5544	$151.55	$151.55	$151.60
7 purchase totals =	$793.61		$837.8170	$837.82	$837.85	$837.80