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	$76.59	8.199%	$82.8696	$82.87	$82.85	$82.90
Purchase #2	$118.27	11.272%	$131.6014	$131.60	$131.60	$131.60
Purchase #3	$35.79	4.843%	$37.5233	$37.52	$37.50	$37.50
Purchase #4	$222.34	4.300%	$231.9006	$231.90	$231.90	$231.90
Purchase #5	$81.26	13.402%	$92.1505	$92.15	$92.15	$92.20
Purchase #6	$89.58	5.592%	$94.5893	$94.59	$94.60	$94.60
Purchase #7	$146.86	5.121%	$154.3807	$154.38	$154.40	$154.40
7 purchase totals =	$770.69		$825.0154	$825.01	$825.00	$825.10