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	$140.59	8.552%	$152.6133	$152.61	$152.60	$152.60
Purchase #2	$165.47	12.846%	$186.7263	$186.73	$186.75	$186.70
Purchase #3	$227.87	8.274%	$246.724	$246.72	$246.70	$246.70
Purchase #4	$238.79	6.515%	$254.3472	$254.35	$254.35	$254.30
Purchase #5	$200.37	13.254%	$226.927	$226.93	$226.95	$226.90
Purchase #6	$114.35	8.289%	$123.8285	$123.83	$123.85	$123.80
Purchase #7	$28.26	11.549%	$31.5237	$31.52	$31.50	$31.50
7 purchase totals =	$1,115.70		$1,222.6900	$1,222.69	$1,222.70	$1,222.50