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	$158.88	8.843%	$172.9298	$172.93	$172.95	$172.90
Purchase #2	$50.74	5.261%	$53.4094	$53.41	$53.40	$53.40
Purchase #3	$224.38	3.362%	$231.9237	$231.92	$231.90	$231.90
Purchase #4	$18.97	10.349%	$20.9332	$20.93	$20.95	$20.90
Purchase #5	$188.63	9.178%	$205.9425	$205.94	$205.95	$205.90
Purchase #6	$43.55	3.583%	$45.1104	$45.11	$45.10	$45.10
Purchase #7	$20.74	5.692%	$21.9205	$21.92	$21.90	$21.90
7 purchase totals =	$705.89		$752.1695	$752.16	$752.15	$752.00