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	$43.59	5.120%	$45.8218	$45.82	$45.80	$45.80
Purchase #2	$48.26	13.672%	$54.8581	$54.86	$54.85	$54.90
Purchase #3	$183.93	12.365%	$206.6729	$206.67	$206.65	$206.70
Purchase #4	$68.25	10.353%	$75.3159	$75.32	$75.30	$75.30
Purchase #5	$95.49	10.342%	$105.3656	$105.37	$105.35	$105.40
Purchase #6	$60.27	7.276%	$64.6552	$64.66	$64.65	$64.70
Purchase #7	$230.27	11.238%	$256.1477	$256.15	$256.15	$256.10
7 purchase totals =	$730.06		$808.8372	$808.85	$808.75	$808.90