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	$85.64	11.548%	$95.5297	$95.53	$95.55	$95.50
Purchase #2	$183.27	13.146%	$207.3627	$207.36	$207.35	$207.40
Purchase #3	$159.30	13.479%	$180.772	$180.77	$180.75	$180.80
Purchase #4	$95.78	5.354%	$100.9081	$100.91	$100.90	$100.90
Purchase #5	$12.65	5.801%	$13.3838	$13.38	$13.40	$13.40
Purchase #6	$95.68	6.511%	$101.9097	$101.91	$101.90	$101.90
Purchase #7	$78.34	5.833%	$82.9096	$82.91	$82.90	$82.90
7 purchase totals =	$710.66		$782.7756	$782.77	$782.75	$782.80