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	$155.88	8.319%	$168.8477	$168.85	$168.85	$168.80
Purchase #2	$83.35	13.118%	$94.2839	$94.28	$94.30	$94.30
Purchase #3	$151.84	4.566%	$158.773	$158.77	$158.75	$158.80
Purchase #4	$135.48	7.431%	$145.5475	$145.55	$145.55	$145.50
Purchase #5	$46.64	7.724%	$50.2425	$50.24	$50.25	$50.20
Purchase #6	$100.52	4.432%	$104.975	$104.98	$105.00	$105.00
Purchase #7	$64.80	13.275%	$73.4022	$73.40	$73.40	$73.40
7 purchase totals =	$738.51		$796.0718	$796.07	$796.10	$796.00