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	$85.64	9.798%	$94.031	$94.03	$94.05	$94.00
Purchase #2	$231.50	11.624%	$258.4096	$258.41	$258.40	$258.40
Purchase #3	$126.94	6.172%	$134.7747	$134.77	$134.75	$134.80
Purchase #4	$89.86	11.665%	$100.3422	$100.34	$100.35	$100.30
Purchase #5	$127.68	6.570%	$136.0686	$136.07	$136.05	$136.10
Purchase #6	$21.69	5.502%	$22.8834	$22.88	$22.90	$22.90
Purchase #7	$109.56	10.107%	$120.6332	$120.63	$120.65	$120.60
7 purchase totals =	$792.87		$867.1427	$867.13	$867.15	$867.10