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	$36.48	4.161%	$37.9979	$38.00	$38.00	$38.00
Purchase #2	$85.58	8.188%	$92.5873	$92.59	$92.60	$92.60
Purchase #3	$186.61	3.216%	$192.6114	$192.61	$192.60	$192.60
Purchase #4	$167.54	9.167%	$182.8984	$182.90	$182.90	$182.90
Purchase #5	$68.50	6.110%	$72.6854	$72.69	$72.70	$72.70
Purchase #6	$92.77	13.538%	$105.3292	$105.33	$105.35	$105.30
Purchase #7	$218.25	6.441%	$232.3075	$232.31	$232.30	$232.30
7 purchase totals =	$855.73		$916.4171	$916.43	$916.45	$916.40