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	$73.67	12.801%	$83.1005	$83.10	$83.10	$83.10
Purchase #2	$242.76	4.394%	$253.4269	$253.43	$253.45	$253.40
Purchase #3	$168.34	12.480%	$189.3488	$189.35	$189.35	$189.30
Purchase #4	$63.83	12.431%	$71.7647	$71.76	$71.75	$71.80
Purchase #5	$197.94	12.715%	$223.1081	$223.11	$223.10	$223.10
Purchase #6	$65.30	9.300%	$71.3729	$71.37	$71.35	$71.40
Purchase #7	$144.43	13.347%	$163.7071	$163.71	$163.70	$163.70
7 purchase totals =	$956.27		$1,055.8290	$1,055.83	$1,055.80	$1,055.80