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	$88.60	3.323%	$91.5442	$91.54	$91.55	$91.50
Purchase #2	$159.39	13.494%	$180.8981	$180.90	$180.90	$180.90
Purchase #3	$14.55	8.508%	$15.7879	$15.79	$15.80	$15.80
Purchase #4	$86.57	6.670%	$92.3442	$92.34	$92.35	$92.30
Purchase #5	$175.28	7.146%	$187.8055	$187.81	$187.80	$187.80
Purchase #6	$134.87	13.313%	$152.8252	$152.83	$152.85	$152.80
Purchase #7	$30.89	8.583%	$33.5413	$33.54	$33.55	$33.50
7 purchase totals =	$690.15		$754.7464	$754.75	$754.80	$754.60