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	$214.63	8.350%	$232.5516	$232.55	$232.55	$232.60
Purchase #2	$138.59	13.227%	$156.9213	$156.92	$156.90	$156.90
Purchase #3	$83.41	11.441%	$92.9529	$92.95	$92.95	$93.00
Purchase #4	$112.53	13.306%	$127.5032	$127.50	$127.50	$127.50
Purchase #5	$246.75	13.284%	$279.5283	$279.53	$279.55	$279.50
Purchase #6	$94.47	6.722%	$100.8203	$100.82	$100.80	$100.80
Purchase #7	$186.87	10.489%	$206.4708	$206.47	$206.45	$206.50
7 purchase totals =	$1,077.25		$1,196.7484	$1,196.74	$1,196.70	$1,196.80