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	$73.27	12.289%	$82.2742	$82.27	$82.25	$82.30
Purchase #2	$61.79	9.688%	$67.7762	$67.78	$67.80	$67.80
Purchase #3	$69.92	12.536%	$78.6852	$78.69	$78.70	$78.70
Purchase #4	$78.97	11.174%	$87.7941	$87.79	$87.80	$87.80
Purchase #5	$117.41	10.527%	$129.7698	$129.77	$129.75	$129.80
Purchase #6	$101.89	12.367%	$114.4907	$114.49	$114.50	$114.50
Purchase #7	$68.39	7.451%	$73.4857	$73.49	$73.50	$73.50
7 purchase totals =	$571.64		$634.2759	$634.28	$634.30	$634.40