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	$126.62	6.182%	$134.4476	$134.45	$134.45	$134.40
Purchase #2	$59.49	8.152%	$64.3396	$64.34	$64.35	$64.30
Purchase #3	$29.35	10.801%	$32.5201	$32.52	$32.50	$32.50
Purchase #4	$109.38	6.769%	$116.7839	$116.78	$116.80	$116.80
Purchase #5	$227.81	6.859%	$243.4355	$243.44	$243.45	$243.40
Purchase #6	$7.39	4.392%	$7.7146	$7.71	$7.70	$7.70
Purchase #7	$140.90	4.808%	$147.6745	$147.67	$147.65	$147.70
7 purchase totals =	$700.94		$746.9158	$746.91	$746.90	$746.80