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	$43.50	5.754%	$46.003	$46.00	$46.00	$46.00
Purchase #2	$87.27	5.299%	$91.8944	$91.89	$91.90	$91.90
Purchase #3	$31.65	5.793%	$33.4835	$33.48	$33.50	$33.50
Purchase #4	$134.68	5.441%	$142.0079	$142.01	$142.00	$142.00
Purchase #5	$136.32	7.445%	$146.469	$146.47	$146.45	$146.50
Purchase #6	$230.65	5.729%	$243.8639	$243.86	$243.85	$243.90
Purchase #7	$20.81	12.770%	$23.4674	$23.47	$23.45	$23.50
7 purchase totals =	$684.88		$727.1891	$727.18	$727.15	$727.30