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	$140.66	5.136%	$147.8843	$147.88	$147.90	$147.90
Purchase #2	$57.38	4.534%	$59.9816	$59.98	$60.00	$60.00
Purchase #3	$135.38	4.274%	$141.1661	$141.17	$141.15	$141.20
Purchase #4	$47.43	5.814%	$50.1876	$50.19	$50.20	$50.20
Purchase #5	$33.36	13.583%	$37.8913	$37.89	$37.90	$37.90
Purchase #6	$18.66	10.247%	$20.5721	$20.57	$20.55	$20.60
Purchase #7	$241.74	9.520%	$264.7536	$264.75	$264.75	$264.80
7 purchase totals =	$674.61		$722.4366	$722.43	$722.45	$722.60