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	$204.73	3.287%	$211.4595	$211.46	$211.45	$211.50
Purchase #2	$31.47	12.758%	$35.4849	$35.48	$35.50	$35.50
Purchase #3	$236.26	7.440%	$253.8377	$253.84	$253.85	$253.80
Purchase #4	$12.74	7.577%	$13.7053	$13.71	$13.70	$13.70
Purchase #5	$73.42	11.491%	$81.8567	$81.86	$81.85	$81.90
Purchase #6	$92.79	13.591%	$105.4011	$105.40	$105.40	$105.40
Purchase #7	$247.37	3.278%	$255.4788	$255.48	$255.50	$255.50
7 purchase totals =	$898.78		$957.2240	$957.23	$957.25	$957.30