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	$74.60	4.470%	$77.9346	$77.93	$77.95	$77.90
Purchase #2	$211.44	7.431%	$227.1521	$227.15	$227.15	$227.20
Purchase #3	$89.45	11.342%	$99.5954	$99.60	$99.60	$99.60
Purchase #4	$121.69	12.483%	$136.8806	$136.88	$136.90	$136.90
Purchase #5	$122.40	7.510%	$131.5922	$131.59	$131.60	$131.60
Purchase #6	$6.78	7.579%	$7.2939	$7.29	$7.30	$7.30
Purchase #7	$233.42	4.555%	$244.0523	$244.05	$244.05	$244.10
7 purchase totals =	$859.78		$924.5011	$924.49	$924.55	$924.60