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	$215.41	6.628%	$229.6874	$229.69	$229.70	$229.70
Purchase #2	$123.47	10.245%	$136.1195	$136.12	$136.10	$136.10
Purchase #3	$189.69	3.117%	$195.6026	$195.60	$195.60	$195.60
Purchase #4	$231.95	4.473%	$242.3251	$242.33	$242.35	$242.30
Purchase #5	$203.84	5.132%	$214.3011	$214.30	$214.30	$214.30
Purchase #6	$100.72	10.378%	$111.1727	$111.17	$111.15	$111.20
Purchase #7	$211.86	8.481%	$229.8278	$229.83	$229.85	$229.80
7 purchase totals =	$1,276.94		$1,359.0362	$1,359.04	$1,359.05	$1,359.00