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	$246.33	6.550%	$262.4646	$262.46	$262.45	$262.50
Purchase #2	$165.50	13.159%	$187.2781	$187.28	$187.30	$187.30
Purchase #3	$105.30	8.778%	$114.5432	$114.54	$114.55	$114.50
Purchase #4	$22.31	5.842%	$23.6134	$23.61	$23.60	$23.60
Purchase #5	$121.85	7.110%	$130.5135	$130.51	$130.50	$130.50
Purchase #6	$150.98	9.546%	$165.3926	$165.39	$165.40	$165.40
Purchase #7	$39.46	5.617%	$41.6765	$41.68	$41.70	$41.70
7 purchase totals =	$851.73		$925.4819	$925.47	$925.50	$925.50