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	$60.29	5.851%	$63.8176	$63.82	$63.80	$63.80
Purchase #2	$230.82	8.521%	$250.4882	$250.49	$250.50	$250.50
Purchase #3	$13.71	5.377%	$14.4472	$14.45	$14.45	$14.40
Purchase #4	$57.61	3.350%	$59.5399	$59.54	$59.55	$59.50
Purchase #5	$81.83	4.653%	$85.6375	$85.64	$85.65	$85.60
Purchase #6	$130.52	10.248%	$143.8957	$143.90	$143.90	$143.90
Purchase #7	$130.63	13.144%	$147.8	$147.80	$147.80	$147.80
7 purchase totals =	$705.41		$765.6261	$765.64	$765.65	$765.50