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	$62.25	13.819%	$70.8523	$70.85	$70.85	$70.90
Purchase #2	$96.94	4.839%	$101.6309	$101.63	$101.65	$101.60
Purchase #3	$50.50	13.473%	$57.3039	$57.30	$57.30	$57.30
Purchase #4	$147.71	10.147%	$162.6981	$162.70	$162.70	$162.70
Purchase #5	$33.53	11.390%	$37.3491	$37.35	$37.35	$37.30
Purchase #6	$142.97	8.736%	$155.4599	$155.46	$155.45	$155.50
Purchase #7	$244.64	7.599%	$263.2302	$263.23	$263.25	$263.20
7 purchase totals =	$778.54		$848.5244	$848.52	$848.55	$848.50