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	$239.59	9.246%	$261.7425	$261.74	$261.75	$261.70
Purchase #2	$42.82	7.321%	$45.9549	$45.95	$45.95	$46.00
Purchase #3	$143.94	12.167%	$161.4532	$161.45	$161.45	$161.50
Purchase #4	$101.56	6.610%	$108.2731	$108.27	$108.25	$108.30
Purchase #5	$141.56	13.819%	$161.1222	$161.12	$161.10	$161.10
Purchase #6	$35.66	6.325%	$37.9155	$37.92	$37.90	$37.90
Purchase #7	$223.73	13.853%	$254.7233	$254.72	$254.70	$254.70
7 purchase totals =	$928.86		$1,031.1847	$1,031.17	$1,031.10	$1,031.20