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	$101.38	12.868%	$114.4256	$114.43	$114.45	$114.40
Purchase #2	$59.51	12.524%	$66.963	$66.96	$66.95	$67.00
Purchase #3	$116.31	12.275%	$130.5871	$130.59	$130.60	$130.60
Purchase #4	$216.71	5.738%	$229.1448	$229.14	$229.15	$229.10
Purchase #5	$147.64	10.303%	$162.8513	$162.85	$162.85	$162.90
Purchase #6	$135.96	13.110%	$153.7844	$153.78	$153.80	$153.80
Purchase #7	$239.31	10.709%	$264.9377	$264.94	$264.95	$264.90
7 purchase totals =	$1,016.82		$1,122.6939	$1,122.69	$1,122.75	$1,122.70