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	$92.57	13.539%	$105.1031	$105.10	$105.10	$105.10
Purchase #2	$30.43	3.459%	$31.4826	$31.48	$31.50	$31.50
Purchase #3	$159.91	3.288%	$165.1678	$165.17	$165.15	$165.20
Purchase #4	$37.67	13.288%	$42.6756	$42.68	$42.70	$42.70
Purchase #5	$28.55	3.292%	$29.4899	$29.49	$29.50	$29.50
Purchase #6	$137.98	13.704%	$156.8888	$156.89	$156.90	$156.90
Purchase #7	$84.38	11.286%	$93.9031	$93.90	$93.90	$93.90
7 purchase totals =	$571.49		$624.7109	$624.71	$624.75	$624.80