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	$31.40	3.161%	$32.3926	$32.39	$32.40	$32.40
Purchase #2	$30.35	4.196%	$31.6235	$31.62	$31.60	$31.60
Purchase #3	$195.82	10.559%	$216.4966	$216.50	$216.50	$216.50
Purchase #4	$124.85	7.711%	$134.4772	$134.48	$134.50	$134.50
Purchase #5	$18.60	10.774%	$20.604	$20.60	$20.60	$20.60
Purchase #6	$215.63	3.773%	$223.7657	$223.77	$223.75	$223.80
Purchase #7	$34.66	3.470%	$35.8627	$35.86	$35.85	$35.90
7 purchase totals =	$651.31		$695.2223	$695.22	$695.20	$695.30