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	$145.34	3.150%	$149.9182	$149.92	$149.90	$149.90
Purchase #2	$113.42	11.800%	$126.8036	$126.80	$126.80	$126.80
Purchase #3	$121.25	5.122%	$127.4604	$127.46	$127.45	$127.50
Purchase #4	$92.66	13.756%	$105.4063	$105.41	$105.40	$105.40
Purchase #5	$89.27	7.799%	$96.2322	$96.23	$96.25	$96.20
Purchase #6	$227.55	8.357%	$246.5664	$246.57	$246.55	$246.60
Purchase #7	$85.25	4.445%	$89.0394	$89.04	$89.05	$89.00
7 purchase totals =	$874.74		$941.4265	$941.43	$941.40	$941.40