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	$203.81	7.609%	$219.3179	$219.32	$219.30	$219.30
Purchase #2	$219.93	3.631%	$227.9157	$227.92	$227.90	$227.90
Purchase #3	$239.86	9.338%	$262.2581	$262.26	$262.25	$262.30
Purchase #4	$42.53	7.508%	$45.7232	$45.72	$45.70	$45.70
Purchase #5	$18.89	9.657%	$20.7142	$20.71	$20.70	$20.70
Purchase #6	$206.93	7.496%	$222.4415	$222.44	$222.45	$222.40
Purchase #7	$246.92	7.578%	$265.6316	$265.63	$265.65	$265.60
7 purchase totals =	$1,178.87		$1,264.0022	$1,264.00	$1,263.95	$1,263.90