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	$217.45	9.746%	$238.6427	$238.64	$238.65	$238.60
Purchase #2	$7.35	7.111%	$7.8727	$7.87	$7.85	$7.90
Purchase #3	$184.69	5.659%	$195.1416	$195.14	$195.15	$195.10
Purchase #4	$75.36	9.111%	$82.226	$82.23	$82.25	$82.20
Purchase #5	$149.68	12.513%	$168.4095	$168.41	$168.40	$168.40
Purchase #6	$125.78	11.236%	$139.9126	$139.91	$139.90	$139.90
Purchase #7	$97.43	3.514%	$100.8537	$100.85	$100.85	$100.90
7 purchase totals =	$857.74		$933.0588	$933.05	$933.05	$933.00