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	$222.29	4.866%	$233.1066	$233.11	$233.10	$233.10
Purchase #2	$232.71	13.504%	$264.1352	$264.14	$264.15	$264.10
Purchase #3	$230.96	11.529%	$257.5874	$257.59	$257.60	$257.60
Purchase #4	$15.70	9.459%	$17.1851	$17.19	$17.20	$17.20
Purchase #5	$101.47	7.490%	$109.0701	$109.07	$109.05	$109.10
Purchase #6	$235.65	4.618%	$246.5323	$246.53	$246.55	$246.50
Purchase #7	$241.54	13.364%	$273.8194	$273.82	$273.80	$273.80
7 purchase totals =	$1,280.32		$1,401.4361	$1,401.45	$1,401.45	$1,401.40