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	$185.45	6.413%	$197.3429	$197.34	$197.35	$197.30
Purchase #2	$181.56	8.358%	$196.7348	$196.73	$196.75	$196.70
Purchase #3	$226.67	6.402%	$241.1814	$241.18	$241.20	$241.20
Purchase #4	$188.59	8.742%	$205.0765	$205.08	$205.10	$205.10
Purchase #5	$59.53	11.835%	$66.5754	$66.58	$66.60	$66.60
Purchase #6	$153.31	11.745%	$171.3163	$171.32	$171.30	$171.30
Purchase #7	$208.27	6.845%	$222.5261	$222.53	$222.55	$222.50
7 purchase totals =	$1,203.38		$1,300.7534	$1,300.76	$1,300.85	$1,300.70