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	$185.98	3.116%	$191.7751	$191.78	$191.80	$191.80
Purchase #2	$152.44	11.479%	$169.9386	$169.94	$169.95	$169.90
Purchase #3	$128.71	12.246%	$144.4718	$144.47	$144.45	$144.50
Purchase #4	$182.31	7.324%	$195.6624	$195.66	$195.65	$195.70
Purchase #5	$86.32	12.164%	$96.82	$96.82	$96.80	$96.80
Purchase #6	$141.46	4.610%	$147.9813	$147.98	$148.00	$148.00
Purchase #7	$13.74	13.505%	$15.5956	$15.60	$15.60	$15.60
7 purchase totals =	$890.96		$962.2448	$962.25	$962.25	$962.30