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	$90.83	8.807%	$98.8294	$98.83	$98.85	$98.80
Purchase #2	$160.45	5.439%	$169.1769	$169.18	$169.20	$169.20
Purchase #3	$109.71	3.222%	$113.2449	$113.24	$113.25	$113.20
Purchase #4	$204.25	3.130%	$210.643	$210.64	$210.65	$210.60
Purchase #5	$40.90	4.436%	$42.7143	$42.71	$42.70	$42.70
Purchase #6	$61.28	10.501%	$67.715	$67.72	$67.70	$67.70
Purchase #7	$243.64	6.851%	$260.3318	$260.33	$260.35	$260.30
7 purchase totals =	$911.06		$962.6553	$962.65	$962.70	$962.50