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	$67.74	9.495%	$74.1719	$74.17	$74.15	$74.20
Purchase #2	$126.83	10.271%	$139.8567	$139.86	$139.85	$139.90
Purchase #3	$228.80	8.661%	$248.6164	$248.62	$248.60	$248.60
Purchase #4	$87.38	13.795%	$99.4341	$99.43	$99.45	$99.40
Purchase #5	$12.50	6.480%	$13.31	$13.31	$13.30	$13.30
Purchase #6	$60.72	11.263%	$67.5589	$67.56	$67.55	$67.60
Purchase #7	$51.82	13.775%	$58.9582	$58.96	$58.95	$59.00
7 purchase totals =	$635.79		$701.9062	$701.91	$701.85	$702.00