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	$63.36	13.403%	$71.8521	$71.85	$71.85	$71.90
Purchase #2	$62.59	6.845%	$66.8743	$66.87	$66.85	$66.90
Purchase #3	$162.30	12.693%	$182.9007	$182.90	$182.90	$182.90
Purchase #4	$204.58	7.252%	$219.4161	$219.42	$219.40	$219.40
Purchase #5	$96.61	13.655%	$109.8021	$109.80	$109.80	$109.80
Purchase #6	$209.62	8.536%	$227.5132	$227.51	$227.50	$227.50
Purchase #7	$89.30	6.466%	$95.0741	$95.07	$95.05	$95.10
7 purchase totals =	$888.36		$973.4326	$973.42	$973.35	$973.50