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	$149.25	12.867%	$168.454	$168.45	$168.45	$168.50
Purchase #2	$76.67	7.696%	$82.5705	$82.57	$82.55	$82.60
Purchase #3	$52.74	12.868%	$59.5266	$59.53	$59.55	$59.50
Purchase #4	$67.49	10.196%	$74.3713	$74.37	$74.35	$74.40
Purchase #5	$215.73	13.701%	$245.2872	$245.29	$245.30	$245.30
Purchase #6	$109.39	4.334%	$114.131	$114.13	$114.15	$114.10
Purchase #7	$179.51	13.392%	$203.55	$203.55	$203.55	$203.60
7 purchase totals =	$850.78		$947.8906	$947.89	$947.90	$948.00