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	$199.59	5.465%	$210.4976	$210.50	$210.50	$210.50
Purchase #2	$141.74	9.620%	$155.3754	$155.38	$155.40	$155.40
Purchase #3	$51.56	6.221%	$54.7675	$54.77	$54.75	$54.80
Purchase #4	$28.62	12.849%	$32.2974	$32.30	$32.30	$32.30
Purchase #5	$19.33	6.445%	$20.5758	$20.58	$20.60	$20.60
Purchase #6	$243.85	4.601%	$255.0695	$255.07	$255.05	$255.10
Purchase #7	$208.94	11.518%	$233.0057	$233.01	$233.00	$233.00
7 purchase totals =	$893.63		$961.5889	$961.61	$961.60	$961.70