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	$59.35	4.340%	$61.9258	$61.93	$61.95	$61.90
Purchase #2	$212.46	5.143%	$223.3868	$223.39	$223.40	$223.40
Purchase #3	$49.26	13.467%	$55.8938	$55.89	$55.90	$55.90
Purchase #4	$48.33	7.231%	$51.8247	$51.82	$51.80	$51.80
Purchase #5	$29.92	11.825%	$33.458	$33.46	$33.45	$33.50
Purchase #6	$86.27	12.178%	$96.776	$96.78	$96.80	$96.80
Purchase #7	$135.54	10.531%	$149.8137	$149.81	$149.80	$149.80
7 purchase totals =	$621.13		$673.0788	$673.08	$673.10	$673.10