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	$13.60	5.570%	$14.3575	$14.36	$14.35	$14.40
Purchase #2	$207.87	11.296%	$231.351	$231.35	$231.35	$231.40
Purchase #3	$139.53	3.767%	$144.7861	$144.79	$144.80	$144.80
Purchase #4	$110.71	11.494%	$123.435	$123.44	$123.45	$123.40
Purchase #5	$64.28	12.404%	$72.2533	$72.25	$72.25	$72.30
Purchase #6	$184.33	5.749%	$194.9271	$194.93	$194.95	$194.90
Purchase #7	$30.32	8.474%	$32.8893	$32.89	$32.90	$32.90
7 purchase totals =	$750.64		$813.9993	$814.01	$814.05	$814.10