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	$230.66	6.325%	$245.2492	$245.25	$245.25	$245.20
Purchase #2	$36.27	11.849%	$40.5676	$40.57	$40.55	$40.60
Purchase #3	$157.48	8.434%	$170.7619	$170.76	$170.75	$170.80
Purchase #4	$50.29	6.660%	$53.6393	$53.64	$53.65	$53.60
Purchase #5	$200.87	6.307%	$213.5389	$213.54	$213.55	$213.50
Purchase #6	$84.82	5.595%	$89.5657	$89.57	$89.55	$89.60
Purchase #7	$104.25	8.270%	$112.8715	$112.87	$112.85	$112.90
7 purchase totals =	$864.64		$926.1941	$926.20	$926.15	$926.20