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	$155.47	9.810%	$170.7216	$170.72	$170.70	$170.70
Purchase #2	$102.72	9.533%	$112.5123	$112.51	$112.50	$112.50
Purchase #3	$69.98	3.689%	$72.5616	$72.56	$72.55	$72.60
Purchase #4	$102.49	7.705%	$110.3869	$110.39	$110.40	$110.40
Purchase #5	$111.93	6.798%	$119.539	$119.54	$119.55	$119.50
Purchase #6	$80.60	10.693%	$89.2186	$89.22	$89.20	$89.20
Purchase #7	$243.73	11.651%	$272.127	$272.13	$272.15	$272.10
7 purchase totals =	$866.92		$947.0670	$947.07	$947.05	$947.00