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	$195.44	11.400%	$217.7202	$217.72	$217.70	$217.70
Purchase #2	$136.83	5.146%	$143.8713	$143.87	$143.85	$143.90
Purchase #3	$141.33	8.129%	$152.8187	$152.82	$152.80	$152.80
Purchase #4	$96.87	8.722%	$105.319	$105.32	$105.30	$105.30
Purchase #5	$217.86	13.264%	$246.757	$246.76	$246.75	$246.80
Purchase #6	$97.41	7.255%	$104.4771	$104.48	$104.50	$104.50
Purchase #7	$173.35	12.410%	$194.8627	$194.86	$194.85	$194.90
7 purchase totals =	$1,059.09		$1,165.8260	$1,165.83	$1,165.75	$1,165.90