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	$229.98	8.749%	$250.101	$250.10	$250.10	$250.10
Purchase #2	$12.89	12.527%	$14.5047	$14.50	$14.50	$14.50
Purchase #3	$146.33	12.636%	$164.8203	$164.82	$164.80	$164.80
Purchase #4	$99.63	10.390%	$109.9816	$109.98	$110.00	$110.00
Purchase #5	$225.36	13.229%	$255.1729	$255.17	$255.15	$255.20
Purchase #6	$158.61	7.191%	$170.0156	$170.02	$170.00	$170.00
Purchase #7	$61.34	11.764%	$68.556	$68.56	$68.55	$68.60
7 purchase totals =	$934.14		$1,033.1521	$1,033.15	$1,033.10	$1,033.20