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	$197.57	11.494%	$220.2787	$220.28	$220.30	$220.30
Purchase #2	$90.96	10.828%	$100.8091	$100.81	$100.80	$100.80
Purchase #3	$244.59	8.166%	$264.5632	$264.56	$264.55	$264.60
Purchase #4	$144.45	7.679%	$155.5423	$155.54	$155.55	$155.50
Purchase #5	$30.87	5.253%	$32.4916	$32.49	$32.50	$32.50
Purchase #6	$6.46	7.147%	$6.9217	$6.92	$6.90	$6.90
Purchase #7	$187.34	4.371%	$195.5286	$195.53	$195.55	$195.50
7 purchase totals =	$902.24		$976.1352	$976.13	$976.15	$976.10