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	$158.67	8.186%	$171.6587	$171.66	$171.65	$171.70
Purchase #2	$97.34	8.221%	$105.3423	$105.34	$105.35	$105.30
Purchase #3	$186.62	5.508%	$196.899	$196.90	$196.90	$196.90
Purchase #4	$72.30	9.211%	$78.9596	$78.96	$78.95	$79.00
Purchase #5	$126.74	7.367%	$136.0769	$136.08	$136.10	$136.10
Purchase #6	$52.26	8.412%	$56.6561	$56.66	$56.65	$56.70
Purchase #7	$59.79	3.853%	$62.0937	$62.09	$62.10	$62.10
7 purchase totals =	$753.72		$807.6863	$807.69	$807.70	$807.80