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	$75.86	3.825%	$78.7616	$78.76	$78.75	$78.80
Purchase #2	$197.85	7.869%	$213.4188	$213.42	$213.40	$213.40
Purchase #3	$165.85	8.726%	$180.3221	$180.32	$180.30	$180.30
Purchase #4	$205.26	4.111%	$213.6982	$213.70	$213.70	$213.70
Purchase #5	$199.54	12.248%	$223.9797	$223.98	$224.00	$224.00
Purchase #6	$12.78	5.715%	$13.5104	$13.51	$13.50	$13.50
Purchase #7	$76.32	11.853%	$85.3662	$85.37	$85.35	$85.40
7 purchase totals =	$933.46		$1,009.0570	$1,009.06	$1,009.00	$1,009.10