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	$188.92	11.637%	$210.9046	$210.90	$210.90	$210.90
Purchase #2	$178.51	5.221%	$187.83	$187.83	$187.85	$187.80
Purchase #3	$109.49	10.126%	$120.577	$120.58	$120.60	$120.60
Purchase #4	$85.89	10.118%	$94.5804	$94.58	$94.60	$94.60
Purchase #5	$99.95	3.423%	$103.3713	$103.37	$103.35	$103.40
Purchase #6	$210.95	3.428%	$218.1814	$218.18	$218.20	$218.20
Purchase #7	$147.49	12.802%	$166.3717	$166.37	$166.35	$166.40
7 purchase totals =	$1,021.20		$1,101.8164	$1,101.81	$1,101.85	$1,101.90