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	$162.62	10.576%	$179.8187	$179.82	$179.80	$179.80
Purchase #2	$92.96	8.158%	$100.5437	$100.54	$100.55	$100.50
Purchase #3	$208.31	11.718%	$232.7198	$232.72	$232.70	$232.70
Purchase #4	$45.94	7.210%	$49.2523	$49.25	$49.25	$49.30
Purchase #5	$134.42	12.166%	$150.7735	$150.77	$150.75	$150.80
Purchase #6	$54.25	9.219%	$59.2513	$59.25	$59.25	$59.30
Purchase #7	$153.90	11.708%	$171.9186	$171.92	$171.90	$171.90
7 purchase totals =	$852.40		$944.2779	$944.27	$944.20	$944.30