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	$82.67	4.173%	$86.1198	$86.12	$86.10	$86.10
Purchase #2	$37.28	4.345%	$38.8998	$38.90	$38.90	$38.90
Purchase #3	$147.56	7.866%	$159.1671	$159.17	$159.15	$159.20
Purchase #4	$13.25	11.487%	$14.772	$14.77	$14.75	$14.80
Purchase #5	$13.56	5.656%	$14.327	$14.33	$14.35	$14.30
Purchase #6	$28.98	10.461%	$32.0116	$32.01	$32.00	$32.00
Purchase #7	$94.78	6.231%	$100.6857	$100.69	$100.70	$100.70
7 purchase totals =	$418.08		$445.9830	$445.99	$445.95	$446.00