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	$226.42	7.326%	$243.0075	$243.01	$243.00	$243.00
Purchase #2	$54.73	8.736%	$59.5112	$59.51	$59.50	$59.50
Purchase #3	$122.26	12.393%	$137.4117	$137.41	$137.40	$137.40
Purchase #4	$55.84	6.775%	$59.6232	$59.62	$59.60	$59.60
Purchase #5	$72.39	7.419%	$77.7606	$77.76	$77.75	$77.80
Purchase #6	$44.82	11.165%	$49.8242	$49.82	$49.80	$49.80
Purchase #7	$105.89	10.659%	$117.1768	$117.18	$117.20	$117.20
7 purchase totals =	$682.35		$744.3152	$744.31	$744.25	$744.30