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	$177.77	7.228%	$190.6192	$190.62	$190.60	$190.60
Purchase #2	$61.89	9.759%	$67.9298	$67.93	$67.95	$67.90
Purchase #3	$96.52	3.304%	$99.709	$99.71	$99.70	$99.70
Purchase #4	$230.73	8.330%	$249.9498	$249.95	$249.95	$249.90
Purchase #5	$124.82	9.812%	$137.0673	$137.07	$137.05	$137.10
Purchase #6	$244.73	4.325%	$255.3146	$255.31	$255.30	$255.30
Purchase #7	$168.60	9.672%	$184.907	$184.91	$184.90	$184.90
7 purchase totals =	$1,105.06		$1,185.4967	$1,185.50	$1,185.45	$1,185.40