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	$47.66	10.750%	$52.7835	$52.78	$52.80	$52.80
Purchase #2	$33.89	7.846%	$36.549	$36.55	$36.55	$36.50
Purchase #3	$95.77	7.637%	$103.084	$103.08	$103.10	$103.10
Purchase #4	$118.29	8.359%	$128.1779	$128.18	$128.20	$128.20
Purchase #5	$68.83	3.328%	$71.1207	$71.12	$71.10	$71.10
Purchase #6	$77.50	6.480%	$82.522	$82.52	$82.50	$82.50
Purchase #7	$15.63	10.546%	$17.2783	$17.28	$17.30	$17.30
7 purchase totals =	$457.57		$491.5154	$491.51	$491.55	$491.50