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	$195.87	7.276%	$210.1215	$210.12	$210.10	$210.10
Purchase #2	$229.56	8.652%	$249.4215	$249.42	$249.40	$249.40
Purchase #3	$51.87	4.800%	$54.3598	$54.36	$54.35	$54.40
Purchase #4	$84.40	7.223%	$90.4962	$90.50	$90.50	$90.50
Purchase #5	$177.85	4.295%	$185.4887	$185.49	$185.50	$185.50
Purchase #6	$169.52	11.782%	$189.4928	$189.49	$189.50	$189.50
Purchase #7	$148.77	5.817%	$157.424	$157.42	$157.40	$157.40
7 purchase totals =	$1,057.84		$1,136.8045	$1,136.80	$1,136.75	$1,136.80