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	$87.34	9.826%	$95.922	$95.92	$95.90	$95.90
Purchase #2	$119.64	6.350%	$127.2371	$127.24	$127.25	$127.20
Purchase #3	$204.35	8.513%	$221.7463	$221.75	$221.75	$221.70
Purchase #4	$72.32	11.333%	$80.516	$80.52	$80.50	$80.50
Purchase #5	$63.72	3.770%	$66.1222	$66.12	$66.10	$66.10
Purchase #6	$67.27	13.721%	$76.5001	$76.50	$76.50	$76.50
Purchase #7	$195.41	9.260%	$213.505	$213.51	$213.50	$213.50
7 purchase totals =	$810.05		$881.5487	$881.56	$881.50	$881.40