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	$156.74	8.823%	$170.5692	$170.57	$170.55	$170.60
Purchase #2	$85.49	4.544%	$89.3747	$89.37	$89.35	$89.40
Purchase #3	$86.94	3.114%	$89.6473	$89.65	$89.65	$89.60
Purchase #4	$179.89	6.539%	$191.653	$191.65	$191.65	$191.70
Purchase #5	$66.82	8.155%	$72.2692	$72.27	$72.25	$72.30
Purchase #6	$89.93	5.665%	$95.0245	$95.02	$95.00	$95.00
Purchase #7	$40.31	8.378%	$43.6872	$43.69	$43.70	$43.70
7 purchase totals =	$706.12		$752.2251	$752.22	$752.15	$752.30