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	$93.63	7.773%	$100.9079	$100.91	$100.90	$100.90
Purchase #2	$88.57	12.786%	$99.8946	$99.89	$99.90	$99.90
Purchase #3	$72.73	12.455%	$81.7885	$81.79	$81.80	$81.80
Purchase #4	$146.76	11.530%	$163.6814	$163.68	$163.70	$163.70
Purchase #5	$245.49	8.145%	$265.4852	$265.49	$265.50	$265.50
Purchase #6	$150.79	5.316%	$158.806	$158.81	$158.80	$158.80
Purchase #7	$142.52	8.472%	$154.5943	$154.59	$154.60	$154.60
7 purchase totals =	$940.49		$1,025.1579	$1,025.16	$1,025.20	$1,025.20