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	$76.93	10.670%	$85.1384	$85.14	$85.15	$85.10
Purchase #2	$124.94	6.191%	$132.675	$132.68	$132.70	$132.70
Purchase #3	$142.82	8.732%	$155.291	$155.29	$155.30	$155.30
Purchase #4	$169.56	13.529%	$192.4998	$192.50	$192.50	$192.50
Purchase #5	$250.41	6.161%	$265.8378	$265.84	$265.85	$265.80
Purchase #6	$143.40	9.410%	$156.8939	$156.89	$156.90	$156.90
Purchase #7	$86.45	5.300%	$91.0319	$91.03	$91.05	$91.00
7 purchase totals =	$994.51		$1,079.3678	$1,079.37	$1,079.45	$1,079.30