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	$33.86	7.361%	$36.3524	$36.35	$36.35	$36.40
Purchase #2	$151.75	13.496%	$172.2302	$172.23	$172.25	$172.20
Purchase #3	$103.46	6.189%	$109.8631	$109.86	$109.85	$109.90
Purchase #4	$46.41	10.712%	$51.3814	$51.38	$51.40	$51.40
Purchase #5	$233.30	13.422%	$264.6135	$264.61	$264.60	$264.60
Purchase #6	$192.47	5.769%	$203.5736	$203.57	$203.55	$203.60
Purchase #7	$237.96	12.459%	$267.6074	$267.61	$267.60	$267.60
7 purchase totals =	$999.21		$1,105.6216	$1,105.61	$1,105.60	$1,105.70