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	$125.55	13.429%	$142.4101	$142.41	$142.40	$142.40
Purchase #2	$11.38	13.724%	$12.9418	$12.94	$12.95	$12.90
Purchase #3	$114.35	12.625%	$128.7867	$128.79	$128.80	$128.80
Purchase #4	$17.46	13.196%	$19.764	$19.76	$19.75	$19.80
Purchase #5	$78.26	10.102%	$86.1658	$86.17	$86.15	$86.20
Purchase #6	$152.71	7.740%	$164.5298	$164.53	$164.55	$164.50
Purchase #7	$112.80	11.301%	$125.5475	$125.55	$125.55	$125.50
7 purchase totals =	$612.51		$680.1457	$680.15	$680.15	$680.10