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	$103.53	12.550%	$116.523	$116.52	$116.50	$116.50
Purchase #2	$60.89	7.612%	$65.5249	$65.52	$65.50	$65.50
Purchase #3	$43.34	3.154%	$44.7069	$44.71	$44.70	$44.70
Purchase #4	$105.40	10.244%	$116.1972	$116.20	$116.20	$116.20
Purchase #5	$34.68	9.288%	$37.9011	$37.90	$37.90	$37.90
Purchase #6	$147.37	13.845%	$167.7734	$167.77	$167.75	$167.80
Purchase #7	$189.73	10.583%	$209.8091	$209.81	$209.80	$209.80
7 purchase totals =	$684.94		$758.4356	$758.43	$758.35	$758.40