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	$66.32	11.369%	$73.8599	$73.86	$73.85	$73.90
Purchase #2	$17.34	4.536%	$18.1265	$18.13	$18.15	$18.10
Purchase #3	$62.58	12.697%	$70.5258	$70.53	$70.55	$70.50
Purchase #4	$189.42	13.428%	$214.8553	$214.86	$214.85	$214.90
Purchase #5	$65.53	8.719%	$71.2436	$71.24	$71.25	$71.20
Purchase #6	$89.85	6.650%	$95.825	$95.83	$95.85	$95.80
Purchase #7	$39.36	9.835%	$43.2311	$43.23	$43.25	$43.20
7 purchase totals =	$530.40		$587.6672	$587.68	$587.75	$587.60