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	$160.58	9.464%	$175.7773	$175.78	$175.80	$175.80
Purchase #2	$103.33	12.623%	$116.3733	$116.37	$116.35	$116.40
Purchase #3	$99.79	11.188%	$110.9545	$110.95	$110.95	$111.00
Purchase #4	$74.34	4.114%	$77.3983	$77.40	$77.40	$77.40
Purchase #5	$82.88	9.730%	$90.9442	$90.94	$90.95	$90.90
Purchase #6	$203.51	5.713%	$215.1365	$215.14	$215.15	$215.10
Purchase #7	$80.83	9.722%	$88.6883	$88.69	$88.70	$88.70
7 purchase totals =	$805.26		$875.2724	$875.27	$875.30	$875.30