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	$242.97	4.531%	$253.979	$253.98	$254.00	$254.00
Purchase #2	$90.99	10.416%	$100.4675	$100.47	$100.45	$100.50
Purchase #3	$181.56	9.663%	$199.1041	$199.10	$199.10	$199.10
Purchase #4	$120.34	6.424%	$128.0706	$128.07	$128.05	$128.10
Purchase #5	$12.51	8.200%	$13.5358	$13.54	$13.55	$13.50
Purchase #6	$115.93	10.313%	$127.8859	$127.89	$127.90	$127.90
Purchase #7	$33.73	11.213%	$37.5121	$37.51	$37.50	$37.50
7 purchase totals =	$798.03		$860.5550	$860.56	$860.55	$860.60