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	$93.26	5.749%	$98.6215	$98.62	$98.60	$98.60
Purchase #2	$66.91	9.725%	$73.417	$73.42	$73.40	$73.40
Purchase #3	$155.96	4.324%	$162.7037	$162.70	$162.70	$162.70
Purchase #4	$81.34	11.480%	$90.6778	$90.68	$90.70	$90.70
Purchase #5	$65.78	10.657%	$72.7902	$72.79	$72.80	$72.80
Purchase #6	$188.69	5.542%	$199.1472	$199.15	$199.15	$199.10
Purchase #7	$94.31	6.193%	$100.1506	$100.15	$100.15	$100.20
7 purchase totals =	$746.25		$797.5080	$797.51	$797.50	$797.50