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	$41.78	10.706%	$46.253	$46.25	$46.25	$46.30
Purchase #2	$183.38	7.204%	$196.5907	$196.59	$196.60	$196.60
Purchase #3	$235.26	11.865%	$263.1736	$263.17	$263.15	$263.20
Purchase #4	$159.66	10.157%	$175.8767	$175.88	$175.90	$175.90
Purchase #5	$212.71	3.235%	$219.5912	$219.59	$219.60	$219.60
Purchase #6	$113.91	7.108%	$122.0067	$122.01	$122.00	$122.00
Purchase #7	$66.52	6.614%	$70.9196	$70.92	$70.90	$70.90
7 purchase totals =	$1,013.22		$1,094.4115	$1,094.41	$1,094.40	$1,094.50