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	$42.36	10.465%	$46.793	$46.79	$46.80	$46.80
Purchase #2	$92.72	3.230%	$95.7149	$95.71	$95.70	$95.70
Purchase #3	$196.55	10.272%	$216.7396	$216.74	$216.75	$216.70
Purchase #4	$94.37	5.344%	$99.4131	$99.41	$99.40	$99.40
Purchase #5	$82.96	7.571%	$89.2409	$89.24	$89.25	$89.20
Purchase #6	$112.40	9.427%	$122.9959	$123.00	$123.00	$123.00
Purchase #7	$120.68	9.551%	$132.2061	$132.21	$132.20	$132.20
7 purchase totals =	$742.04		$803.1035	$803.10	$803.10	$803.00