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	$95.41	3.396%	$98.6501	$98.65	$98.65	$98.70
Purchase #2	$125.84	6.383%	$133.8724	$133.87	$133.85	$133.90
Purchase #3	$49.50	4.313%	$51.6349	$51.63	$51.65	$51.60
Purchase #4	$165.73	6.105%	$175.8478	$175.85	$175.85	$175.80
Purchase #5	$121.56	4.580%	$127.1274	$127.13	$127.15	$127.10
Purchase #6	$76.80	7.646%	$82.6721	$82.67	$82.65	$82.70
Purchase #7	$79.69	4.681%	$83.4203	$83.42	$83.40	$83.40
7 purchase totals =	$714.53		$753.2250	$753.22	$753.20	$753.20