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	$65.42	7.765%	$70.4999	$70.50	$70.50	$70.50
Purchase #2	$65.95	10.526%	$72.8919	$72.89	$72.90	$72.90
Purchase #3	$44.56	11.363%	$49.6234	$49.62	$49.60	$49.60
Purchase #4	$171.42	10.599%	$189.5888	$189.59	$189.60	$189.60
Purchase #5	$248.79	10.277%	$274.3581	$274.36	$274.35	$274.40
Purchase #6	$91.71	10.275%	$101.1332	$101.13	$101.15	$101.10
Purchase #7	$199.91	4.121%	$208.1483	$208.15	$208.15	$208.10
7 purchase totals =	$887.76		$966.2436	$966.24	$966.25	$966.20