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	$168.52	13.280%	$190.8995	$190.90	$190.90	$190.90
Purchase #2	$217.90	4.124%	$226.8862	$226.89	$226.90	$226.90
Purchase #3	$167.71	13.546%	$190.428	$190.43	$190.45	$190.40
Purchase #4	$138.73	11.530%	$154.7256	$154.73	$154.75	$154.70
Purchase #5	$65.64	9.360%	$71.7839	$71.78	$71.80	$71.80
Purchase #6	$162.86	8.865%	$177.2975	$177.30	$177.30	$177.30
Purchase #7	$21.28	5.643%	$22.4808	$22.48	$22.50	$22.50
7 purchase totals =	$942.64		$1,034.5015	$1,034.51	$1,034.60	$1,034.50