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	$79.51	7.672%	$85.61	$85.61	$85.60	$85.60
Purchase #2	$84.87	4.135%	$88.3794	$88.38	$88.40	$88.40
Purchase #3	$234.83	3.176%	$242.2882	$242.29	$242.30	$242.30
Purchase #4	$243.97	12.176%	$273.6758	$273.68	$273.70	$273.70
Purchase #5	$56.87	5.214%	$59.8352	$59.84	$59.85	$59.80
Purchase #6	$178.83	11.642%	$199.6494	$199.65	$199.65	$199.60
Purchase #7	$46.87	11.834%	$52.4166	$52.42	$52.40	$52.40
7 purchase totals =	$925.75		$1,001.8546	$1,001.87	$1,001.90	$1,001.80