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	$199.48	11.165%	$221.7519	$221.75	$221.75	$221.80
Purchase #2	$15.87	4.865%	$16.6421	$16.64	$16.65	$16.60
Purchase #3	$198.46	3.788%	$205.9777	$205.98	$206.00	$206.00
Purchase #4	$123.89	12.595%	$139.4939	$139.49	$139.50	$139.50
Purchase #5	$78.35	4.820%	$82.1265	$82.13	$82.15	$82.10
Purchase #6	$35.55	13.730%	$40.431	$40.43	$40.45	$40.40
Purchase #7	$34.43	6.379%	$36.6263	$36.63	$36.65	$36.60
7 purchase totals =	$686.03		$743.0494	$743.05	$743.15	$743.00