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	$135.52	7.792%	$146.0797	$146.08	$146.10	$146.10
Purchase #2	$198.27	4.205%	$206.6073	$206.61	$206.60	$206.60
Purchase #3	$9.87	13.130%	$11.1659	$11.17	$11.15	$11.20
Purchase #4	$61.44	4.466%	$64.1839	$64.18	$64.20	$64.20
Purchase #5	$93.58	12.360%	$105.1465	$105.15	$105.15	$105.10
Purchase #6	$54.45	8.566%	$59.1142	$59.11	$59.10	$59.10
Purchase #7	$85.61	8.419%	$92.8175	$92.82	$92.80	$92.80
7 purchase totals =	$638.74		$685.1150	$685.12	$685.10	$685.10