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	$7.37	3.308%	$7.6138	$7.61	$7.60	$7.60
Purchase #2	$78.42	9.288%	$85.7036	$85.70	$85.70	$85.70
Purchase #3	$192.90	5.332%	$203.1854	$203.19	$203.20	$203.20
Purchase #4	$238.50	8.832%	$259.5643	$259.56	$259.55	$259.60
Purchase #5	$148.85	4.693%	$155.8355	$155.84	$155.85	$155.80
Purchase #6	$182.69	4.756%	$191.3787	$191.38	$191.40	$191.40
Purchase #7	$185.55	3.161%	$191.4152	$191.42	$191.40	$191.40
7 purchase totals =	$1,034.28		$1,094.6965	$1,094.70	$1,094.70	$1,094.70