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	$75.74	12.247%	$85.0159	$85.02	$85.00	$85.00
Purchase #2	$238.70	9.840%	$262.1881	$262.19	$262.20	$262.20
Purchase #3	$89.25	4.702%	$93.4465	$93.45	$93.45	$93.40
Purchase #4	$233.90	13.251%	$264.8941	$264.89	$264.90	$264.90
Purchase #5	$116.35	8.612%	$126.3701	$126.37	$126.35	$126.40
Purchase #6	$180.58	3.569%	$187.0249	$187.02	$187.00	$187.00
Purchase #7	$90.80	9.701%	$99.6085	$99.61	$99.60	$99.60
7 purchase totals =	$1,025.32		$1,118.5481	$1,118.55	$1,118.50	$1,118.50