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	$184.67	6.303%	$196.3098	$196.31	$196.30	$196.30
Purchase #2	$66.49	8.327%	$72.0266	$72.03	$72.05	$72.00
Purchase #3	$203.43	3.449%	$210.4463	$210.45	$210.45	$210.40
Purchase #4	$231.82	7.629%	$249.5055	$249.51	$249.50	$249.50
Purchase #5	$51.36	13.762%	$58.4282	$58.43	$58.45	$58.40
Purchase #6	$195.83	9.732%	$214.8882	$214.89	$214.90	$214.90
Purchase #7	$25.83	13.816%	$29.3987	$29.40	$29.40	$29.40
7 purchase totals =	$959.43		$1,031.0033	$1,031.02	$1,031.05	$1,030.90