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	$117.51	4.804%	$123.1552	$123.16	$123.15	$123.20
Purchase #2	$11.87	13.238%	$13.4414	$13.44	$13.45	$13.40
Purchase #3	$240.70	11.221%	$267.7089	$267.71	$267.70	$267.70
Purchase #4	$66.94	12.399%	$75.2399	$75.24	$75.25	$75.20
Purchase #5	$150.67	7.749%	$162.3454	$162.35	$162.35	$162.30
Purchase #6	$125.28	4.795%	$131.2872	$131.29	$131.30	$131.30
Purchase #7	$81.47	10.297%	$89.859	$89.86	$89.85	$89.90
7 purchase totals =	$794.44		$863.0370	$863.05	$863.05	$863.00