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	$84.95	12.765%	$95.7939	$95.79	$95.80	$95.80
Purchase #2	$90.89	10.119%	$100.0872	$100.09	$100.10	$100.10
Purchase #3	$16.93	10.687%	$18.7393	$18.74	$18.75	$18.70
Purchase #4	$41.60	3.748%	$43.1592	$43.16	$43.15	$43.20
Purchase #5	$176.64	3.382%	$182.614	$182.61	$182.60	$182.60
Purchase #6	$109.50	13.851%	$124.6668	$124.67	$124.65	$124.70
Purchase #7	$62.61	3.759%	$64.9635	$64.96	$64.95	$65.00
7 purchase totals =	$583.12		$630.0239	$630.02	$630.00	$630.10