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	$130.92	13.550%	$148.6597	$148.66	$148.65	$148.70
Purchase #2	$24.49	13.123%	$27.7038	$27.70	$27.70	$27.70
Purchase #3	$67.84	11.243%	$75.4673	$75.47	$75.45	$75.50
Purchase #4	$87.29	3.234%	$90.113	$90.11	$90.10	$90.10
Purchase #5	$69.78	13.823%	$79.4257	$79.43	$79.45	$79.40
Purchase #6	$171.51	9.340%	$187.529	$187.53	$187.55	$187.50
Purchase #7	$64.34	12.705%	$72.5144	$72.51	$72.50	$72.50
7 purchase totals =	$616.17		$681.4129	$681.41	$681.40	$681.40