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	$14.57	7.260%	$15.6278	$15.63	$15.65	$15.60
Purchase #2	$113.69	3.284%	$117.4236	$117.42	$117.40	$117.40
Purchase #3	$93.29	12.453%	$104.9074	$104.91	$104.90	$104.90
Purchase #4	$79.58	7.333%	$85.4156	$85.42	$85.40	$85.40
Purchase #5	$84.82	6.806%	$90.5928	$90.59	$90.60	$90.60
Purchase #6	$148.53	7.144%	$159.141	$159.14	$159.15	$159.10
Purchase #7	$80.81	3.451%	$83.5988	$83.60	$83.60	$83.60
7 purchase totals =	$615.29		$656.7070	$656.71	$656.70	$656.60