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	$118.72	7.646%	$127.7973	$127.80	$127.80	$127.80
Purchase #2	$52.46	10.717%	$58.0821	$58.08	$58.10	$58.10
Purchase #3	$20.99	8.835%	$22.8445	$22.84	$22.85	$22.80
Purchase #4	$238.26	6.300%	$253.2704	$253.27	$253.25	$253.30
Purchase #5	$215.41	12.576%	$242.5	$242.50	$242.50	$242.50
Purchase #6	$139.26	13.314%	$157.8011	$157.80	$157.80	$157.80
Purchase #7	$144.59	4.129%	$150.5601	$150.56	$150.55	$150.60
7 purchase totals =	$929.69		$1,012.8555	$1,012.85	$1,012.85	$1,012.90