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	$83.61	4.299%	$87.2044	$87.20	$87.20	$87.20
Purchase #2	$19.51	12.202%	$21.8906	$21.89	$21.90	$21.90
Purchase #3	$63.58	13.759%	$72.328	$72.33	$72.35	$72.30
Purchase #4	$8.56	7.764%	$9.2246	$9.22	$9.20	$9.20
Purchase #5	$81.49	11.113%	$90.546	$90.55	$90.55	$90.50
Purchase #6	$144.83	4.682%	$151.6109	$151.61	$151.60	$151.60
Purchase #7	$119.93	3.676%	$124.3386	$124.34	$124.35	$124.30
7 purchase totals =	$521.51		$557.1431	$557.14	$557.15	$557.00