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	$160.81	7.165%	$172.332	$172.33	$172.35	$172.30
Purchase #2	$130.83	5.184%	$137.6122	$137.61	$137.60	$137.60
Purchase #3	$76.57	3.486%	$79.2392	$79.24	$79.25	$79.20
Purchase #4	$235.33	12.398%	$264.5062	$264.51	$264.50	$264.50
Purchase #5	$24.90	10.417%	$27.4938	$27.49	$27.50	$27.50
Purchase #6	$245.64	10.824%	$272.2281	$272.23	$272.25	$272.20
Purchase #7	$63.59	3.366%	$65.7304	$65.73	$65.75	$65.70
7 purchase totals =	$937.67		$1,019.1419	$1,019.14	$1,019.20	$1,019.00