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	$108.68	12.650%	$122.428	$122.43	$122.45	$122.40
Purchase #2	$69.98	4.164%	$72.894	$72.89	$72.90	$72.90
Purchase #3	$201.33	10.568%	$222.6066	$222.61	$222.60	$222.60
Purchase #4	$250.34	10.325%	$276.1876	$276.19	$276.20	$276.20
Purchase #5	$50.92	6.216%	$54.0852	$54.09	$54.10	$54.10
Purchase #6	$136.38	3.412%	$141.0333	$141.03	$141.05	$141.00
Purchase #7	$187.46	3.735%	$194.4616	$194.46	$194.45	$194.50
7 purchase totals =	$1,005.09		$1,083.6963	$1,083.70	$1,083.75	$1,083.70