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	$240.61	11.812%	$269.0309	$269.03	$269.05	$269.00
Purchase #2	$52.50	3.728%	$54.4572	$54.46	$54.45	$54.50
Purchase #3	$97.59	8.692%	$106.0725	$106.07	$106.05	$106.10
Purchase #4	$135.39	10.411%	$149.4855	$149.49	$149.50	$149.50
Purchase #5	$65.85	10.623%	$72.8452	$72.85	$72.85	$72.80
Purchase #6	$171.83	7.237%	$184.2653	$184.27	$184.25	$184.30
Purchase #7	$111.65	6.282%	$118.6639	$118.66	$118.65	$118.70
7 purchase totals =	$875.42		$954.8205	$954.83	$954.80	$954.90