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	$162.27	9.414%	$177.5461	$177.55	$177.55	$177.50
Purchase #2	$119.48	10.570%	$132.109	$132.11	$132.10	$132.10
Purchase #3	$208.99	3.482%	$216.267	$216.27	$216.25	$216.30
Purchase #4	$115.39	12.538%	$129.8576	$129.86	$129.85	$129.90
Purchase #5	$100.92	10.467%	$111.4833	$111.48	$111.50	$111.50
Purchase #6	$77.31	11.776%	$86.414	$86.41	$86.40	$86.40
Purchase #7	$83.58	4.670%	$87.4832	$87.48	$87.50	$87.50
7 purchase totals =	$867.94		$941.1602	$941.16	$941.15	$941.20