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	$134.65	9.603%	$147.5804	$147.58	$147.60	$147.60
Purchase #2	$17.91	10.538%	$19.7974	$19.80	$19.80	$19.80
Purchase #3	$164.59	3.831%	$170.8954	$170.90	$170.90	$170.90
Purchase #4	$15.86	6.805%	$16.9393	$16.94	$16.95	$16.90
Purchase #5	$76.38	7.585%	$82.1734	$82.17	$82.15	$82.20
Purchase #6	$31.51	4.380%	$32.8901	$32.89	$32.90	$32.90
Purchase #7	$226.95	12.421%	$255.1395	$255.14	$255.15	$255.10
7 purchase totals =	$667.85		$725.4155	$725.42	$725.45	$725.40