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	$52.25	4.625%	$54.6666	$54.67	$54.65	$54.70
Purchase #2	$237.77	9.608%	$260.6149	$260.61	$260.60	$260.60
Purchase #3	$40.52	12.265%	$45.4898	$45.49	$45.50	$45.50
Purchase #4	$194.46	3.168%	$200.6205	$200.62	$200.60	$200.60
Purchase #5	$38.26	4.742%	$40.0743	$40.07	$40.05	$40.10
Purchase #6	$155.98	8.842%	$169.7718	$169.77	$169.75	$169.80
Purchase #7	$58.27	10.195%	$64.2106	$64.21	$64.20	$64.20
7 purchase totals =	$777.51		$835.4485	$835.44	$835.35	$835.50