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	$7.29	4.713%	$7.6336	$7.63	$7.65	$7.60
Purchase #2	$240.64	9.440%	$263.3564	$263.36	$263.35	$263.40
Purchase #3	$55.33	11.693%	$61.7997	$61.80	$61.80	$61.80
Purchase #4	$65.71	10.157%	$72.3842	$72.38	$72.40	$72.40
Purchase #5	$202.93	10.365%	$223.9637	$223.96	$223.95	$224.00
Purchase #6	$72.26	8.594%	$78.47	$78.47	$78.45	$78.50
Purchase #7	$137.42	8.561%	$149.1845	$149.18	$149.20	$149.20
7 purchase totals =	$781.58		$856.7921	$856.78	$856.80	$856.90