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	$206.28	6.483%	$219.6531	$219.65	$219.65	$219.70
Purchase #2	$186.87	9.519%	$204.6582	$204.66	$204.65	$204.70
Purchase #3	$60.88	7.568%	$65.4874	$65.49	$65.50	$65.50
Purchase #4	$34.48	7.367%	$37.0201	$37.02	$37.00	$37.00
Purchase #5	$171.71	10.606%	$189.9216	$189.92	$189.90	$189.90
Purchase #6	$221.93	5.736%	$234.6599	$234.66	$234.65	$234.70
Purchase #7	$164.88	4.483%	$172.2716	$172.27	$172.25	$172.30
7 purchase totals =	$1,047.03		$1,123.6719	$1,123.67	$1,123.60	$1,123.80