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	$195.55	10.187%	$215.4707	$215.47	$215.45	$215.50
Purchase #2	$244.50	8.724%	$265.8302	$265.83	$265.85	$265.80
Purchase #3	$40.50	11.116%	$45.002	$45.00	$45.00	$45.00
Purchase #4	$193.78	8.487%	$210.2261	$210.23	$210.25	$210.20
Purchase #5	$104.29	6.682%	$111.2587	$111.26	$111.25	$111.30
Purchase #6	$243.80	11.156%	$270.9983	$271.00	$271.00	$271.00
Purchase #7	$247.55	9.521%	$271.1192	$271.12	$271.10	$271.10
7 purchase totals =	$1,269.97		$1,389.9052	$1,389.91	$1,389.90	$1,389.90