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	$73.83	11.766%	$82.5168	$82.52	$82.50	$82.50
Purchase #2	$158.34	3.634%	$164.0941	$164.09	$164.10	$164.10
Purchase #3	$9.57	13.172%	$10.8306	$10.83	$10.85	$10.80
Purchase #4	$17.63	6.466%	$18.77	$18.77	$18.75	$18.80
Purchase #5	$216.48	7.468%	$232.6467	$232.65	$232.65	$232.60
Purchase #6	$138.28	11.416%	$154.066	$154.07	$154.05	$154.10
Purchase #7	$196.46	7.822%	$211.8271	$211.83	$211.85	$211.80
7 purchase totals =	$810.59		$874.7513	$874.76	$874.75	$874.70