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	$176.80	7.824%	$190.6328	$190.63	$190.65	$190.60
Purchase #2	$66.41	10.407%	$73.3213	$73.32	$73.30	$73.30
Purchase #3	$195.70	5.705%	$206.8647	$206.86	$206.85	$206.90
Purchase #4	$199.33	4.839%	$208.9756	$208.98	$209.00	$209.00
Purchase #5	$91.82	11.735%	$102.5951	$102.60	$102.60	$102.60
Purchase #6	$247.43	3.428%	$255.9119	$255.91	$255.90	$255.90
Purchase #7	$202.91	6.203%	$215.4965	$215.50	$215.50	$215.50
7 purchase totals =	$1,180.40		$1,253.7979	$1,253.80	$1,253.80	$1,253.80