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	$202.53	4.593%	$211.8322	$211.83	$211.85	$211.80
Purchase #2	$126.65	6.485%	$134.8633	$134.86	$134.85	$134.90
Purchase #3	$90.58	13.782%	$103.0637	$103.06	$103.05	$103.10
Purchase #4	$210.51	8.556%	$228.5212	$228.52	$228.50	$228.50
Purchase #5	$53.54	12.761%	$60.3722	$60.37	$60.35	$60.40
Purchase #6	$93.36	5.373%	$98.3762	$98.38	$98.40	$98.40
Purchase #7	$233.87	5.798%	$247.4298	$247.43	$247.45	$247.40
7 purchase totals =	$1,011.04		$1,084.4586	$1,084.45	$1,084.45	$1,084.50