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	$36.76	11.738%	$41.0749	$41.07	$41.05	$41.10
Purchase #2	$31.71	6.817%	$33.8717	$33.87	$33.85	$33.90
Purchase #3	$176.60	3.594%	$182.947	$182.95	$182.95	$182.90
Purchase #4	$70.66	10.800%	$78.2913	$78.29	$78.30	$78.30
Purchase #5	$200.84	10.376%	$221.6792	$221.68	$221.70	$221.70
Purchase #6	$106.51	3.222%	$109.9418	$109.94	$109.95	$109.90
Purchase #7	$100.81	4.563%	$105.41	$105.41	$105.40	$105.40
7 purchase totals =	$723.89		$773.2159	$773.21	$773.20	$773.20