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	$136.63	8.750%	$148.5851	$148.59	$148.60	$148.60
Purchase #2	$145.98	3.690%	$151.3667	$151.37	$151.35	$151.40
Purchase #3	$40.52	7.252%	$43.4585	$43.46	$43.45	$43.50
Purchase #4	$226.80	10.183%	$249.895	$249.90	$249.90	$249.90
Purchase #5	$29.57	10.776%	$32.7565	$32.76	$32.75	$32.80
Purchase #6	$52.43	4.272%	$54.6698	$54.67	$54.65	$54.70
Purchase #7	$224.79	11.132%	$249.8136	$249.81	$249.80	$249.80
7 purchase totals =	$856.72		$930.5452	$930.56	$930.50	$930.70