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	$171.47	10.861%	$190.0934	$190.09	$190.10	$190.10
Purchase #2	$73.66	11.717%	$82.2907	$82.29	$82.30	$82.30
Purchase #3	$196.30	10.106%	$216.1381	$216.14	$216.15	$216.10
Purchase #4	$195.48	13.587%	$222.0399	$222.04	$222.05	$222.00
Purchase #5	$10.56	8.796%	$11.4889	$11.49	$11.50	$11.50
Purchase #6	$172.71	9.302%	$188.7755	$188.78	$188.80	$188.80
Purchase #7	$183.59	8.342%	$198.9051	$198.91	$198.90	$198.90
7 purchase totals =	$1,003.77		$1,109.7316	$1,109.74	$1,109.80	$1,109.70