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	$131.56	9.738%	$144.3713	$144.37	$144.35	$144.40
Purchase #2	$178.90	11.738%	$199.8993	$199.90	$199.90	$199.90
Purchase #3	$249.36	11.183%	$277.2459	$277.25	$277.25	$277.20
Purchase #4	$65.36	13.767%	$74.3581	$74.36	$74.35	$74.40
Purchase #5	$55.34	7.161%	$59.3029	$59.30	$59.30	$59.30
Purchase #6	$82.35	3.445%	$85.187	$85.19	$85.20	$85.20
Purchase #7	$156.70	9.451%	$171.5097	$171.51	$171.50	$171.50
7 purchase totals =	$919.57		$1,011.8742	$1,011.88	$1,011.85	$1,011.90