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	$222.26	6.754%	$237.2714	$237.27	$237.25	$237.30
Purchase #2	$80.36	10.355%	$88.6813	$88.68	$88.70	$88.70
Purchase #3	$91.40	9.428%	$100.0172	$100.02	$100.00	$100.00
Purchase #4	$78.64	10.821%	$87.1496	$87.15	$87.15	$87.10
Purchase #5	$200.31	7.730%	$215.794	$215.79	$215.80	$215.80
Purchase #6	$200.38	9.439%	$219.2939	$219.29	$219.30	$219.30
Purchase #7	$29.47	13.374%	$33.4113	$33.41	$33.40	$33.40
7 purchase totals =	$902.82		$981.6187	$981.61	$981.60	$981.60