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	$75.66	8.794%	$82.3135	$82.31	$82.30	$82.30
Purchase #2	$57.68	13.496%	$65.4645	$65.46	$65.45	$65.50
Purchase #3	$160.72	10.538%	$177.6567	$177.66	$177.65	$177.70
Purchase #4	$72.83	10.846%	$80.7291	$80.73	$80.75	$80.70
Purchase #5	$98.42	11.716%	$109.9509	$109.95	$109.95	$110.00
Purchase #6	$225.62	7.502%	$242.546	$242.55	$242.55	$242.50
Purchase #7	$169.32	3.252%	$174.8263	$174.83	$174.85	$174.80
7 purchase totals =	$860.25		$933.4870	$933.49	$933.50	$933.50