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	$92.49	7.826%	$99.7283	$99.73	$99.75	$99.70
Purchase #2	$17.78	3.754%	$18.4475	$18.45	$18.45	$18.40
Purchase #3	$82.88	13.243%	$93.8558	$93.86	$93.85	$93.90
Purchase #4	$124.25	13.274%	$140.7429	$140.74	$140.75	$140.70
Purchase #5	$48.43	8.455%	$52.5248	$52.52	$52.50	$52.50
Purchase #6	$189.66	4.759%	$198.6859	$198.69	$198.70	$198.70
Purchase #7	$129.56	7.524%	$139.3081	$139.31	$139.30	$139.30
7 purchase totals =	$685.05		$743.2933	$743.30	$743.30	$743.20