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	$182.91	7.681%	$196.9593	$196.96	$196.95	$197.00
Purchase #2	$84.48	12.770%	$95.2681	$95.27	$95.25	$95.30
Purchase #3	$172.94	10.185%	$190.5539	$190.55	$190.55	$190.60
Purchase #4	$162.74	4.396%	$169.8941	$169.89	$169.90	$169.90
Purchase #5	$83.59	10.370%	$92.2583	$92.26	$92.25	$92.30
Purchase #6	$59.64	5.405%	$62.8635	$62.86	$62.85	$62.90
Purchase #7	$114.77	3.540%	$118.8329	$118.83	$118.85	$118.80
7 purchase totals =	$861.07		$926.6301	$926.62	$926.60	$926.80