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	$39.51	8.776%	$42.9774	$42.98	$43.00	$43.00
Purchase #2	$124.29	4.554%	$129.9502	$129.95	$129.95	$130.00
Purchase #3	$101.70	7.181%	$109.0031	$109.00	$109.00	$109.00
Purchase #4	$89.78	4.559%	$93.8731	$93.87	$93.85	$93.90
Purchase #5	$72.73	10.552%	$80.4045	$80.40	$80.40	$80.40
Purchase #6	$97.29	12.273%	$109.2304	$109.23	$109.25	$109.20
Purchase #7	$174.74	12.445%	$196.4864	$196.49	$196.50	$196.50
7 purchase totals =	$700.04		$761.9251	$761.92	$761.95	$762.00