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	$96.43	10.814%	$106.8579	$106.86	$106.85	$106.90
Purchase #2	$61.69	13.793%	$70.1989	$70.20	$70.20	$70.20
Purchase #3	$28.80	8.809%	$31.337	$31.34	$31.35	$31.30
Purchase #4	$106.38	6.658%	$113.4628	$113.46	$113.45	$113.50
Purchase #5	$62.65	4.734%	$65.6159	$65.62	$65.60	$65.60
Purchase #6	$12.88	6.342%	$13.6968	$13.70	$13.70	$13.70
Purchase #7	$91.57	6.103%	$97.1585	$97.16	$97.15	$97.20
7 purchase totals =	$460.40		$498.3278	$498.34	$498.30	$498.40