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	$113.50	12.748%	$127.969	$127.97	$127.95	$128.00
Purchase #2	$220.86	4.691%	$231.2205	$231.22	$231.20	$231.20
Purchase #3	$164.53	12.661%	$185.3611	$185.36	$185.35	$185.40
Purchase #4	$77.29	5.540%	$81.5719	$81.57	$81.55	$81.60
Purchase #5	$79.96	13.328%	$90.6171	$90.62	$90.60	$90.60
Purchase #6	$233.83	8.261%	$253.1467	$253.15	$253.15	$253.10
Purchase #7	$196.31	5.163%	$206.4455	$206.45	$206.45	$206.40
7 purchase totals =	$1,086.28		$1,176.3318	$1,176.34	$1,176.25	$1,176.30