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	$246.67	4.418%	$257.5679	$257.57	$257.55	$257.60
Purchase #2	$240.62	6.707%	$256.7584	$256.76	$256.75	$256.80
Purchase #3	$227.39	10.579%	$251.4456	$251.45	$251.45	$251.40
Purchase #4	$87.86	3.717%	$91.1258	$91.13	$91.15	$91.10
Purchase #5	$83.95	9.425%	$91.8623	$91.86	$91.85	$91.90
Purchase #6	$213.86	13.854%	$243.4882	$243.49	$243.50	$243.50
Purchase #7	$199.83	4.699%	$209.22	$209.22	$209.20	$209.20
7 purchase totals =	$1,300.18		$1,401.4682	$1,401.48	$1,401.45	$1,401.50