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	$11.59	4.333%	$12.0922	$12.09	$12.10	$12.10
Purchase #2	$119.83	3.743%	$124.3152	$124.32	$124.30	$124.30
Purchase #3	$90.55	3.243%	$93.4865	$93.49	$93.50	$93.50
Purchase #4	$242.60	13.773%	$276.0133	$276.01	$276.00	$276.00
Purchase #5	$250.89	9.194%	$273.9568	$273.96	$273.95	$274.00
Purchase #6	$209.33	4.793%	$219.3632	$219.36	$219.35	$219.40
Purchase #7	$166.27	4.413%	$173.6075	$173.61	$173.60	$173.60
7 purchase totals =	$1,091.06		$1,172.8347	$1,172.84	$1,172.80	$1,172.90