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	$169.53	10.773%	$187.7935	$187.79	$187.80	$187.80
Purchase #2	$37.47	8.298%	$40.5793	$40.58	$40.60	$40.60
Purchase #3	$228.62	5.796%	$241.8708	$241.87	$241.85	$241.90
Purchase #4	$87.53	9.467%	$95.8165	$95.82	$95.80	$95.80
Purchase #5	$211.25	4.132%	$219.9789	$219.98	$220.00	$220.00
Purchase #6	$114.62	11.112%	$127.3566	$127.36	$127.35	$127.40
Purchase #7	$133.35	4.702%	$139.6201	$139.62	$139.60	$139.60
7 purchase totals =	$982.37		$1,053.0157	$1,053.02	$1,053.00	$1,053.10