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	$170.89	9.850%	$187.7227	$187.72	$187.70	$187.70
Purchase #2	$198.35	12.344%	$222.8343	$222.83	$222.85	$222.80
Purchase #3	$100.90	11.204%	$112.2048	$112.20	$112.20	$112.20
Purchase #4	$103.50	6.144%	$109.859	$109.86	$109.85	$109.90
Purchase #5	$71.75	6.273%	$76.2509	$76.25	$76.25	$76.30
Purchase #6	$213.67	11.481%	$238.2015	$238.20	$238.20	$238.20
Purchase #7	$225.39	5.293%	$237.3199	$237.32	$237.30	$237.30
7 purchase totals =	$1,084.45		$1,184.3931	$1,184.38	$1,184.35	$1,184.40