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	$28.93	12.717%	$32.609	$32.61	$32.60	$32.60
Purchase #2	$42.79	12.544%	$48.1576	$48.16	$48.15	$48.20
Purchase #3	$154.81	12.678%	$174.4368	$174.44	$174.45	$174.40
Purchase #4	$7.41	8.544%	$8.0431	$8.04	$8.05	$8.00
Purchase #5	$147.65	9.825%	$162.1566	$162.16	$162.15	$162.20
Purchase #6	$91.73	12.572%	$103.2623	$103.26	$103.25	$103.30
Purchase #7	$77.56	5.773%	$82.0375	$82.04	$82.05	$82.00
7 purchase totals =	$550.88		$610.7029	$610.71	$610.70	$610.70