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	$179.33	12.577%	$201.8843	$201.88	$201.90	$201.90
Purchase #2	$237.38	10.118%	$261.3981	$261.40	$261.40	$261.40
Purchase #3	$35.77	7.486%	$38.4477	$38.45	$38.45	$38.40
Purchase #4	$94.47	5.672%	$99.8283	$99.83	$99.85	$99.80
Purchase #5	$117.65	7.441%	$126.4043	$126.40	$126.40	$126.40
Purchase #6	$80.31	6.119%	$85.2242	$85.22	$85.20	$85.20
Purchase #7	$233.87	7.270%	$250.8723	$250.87	$250.85	$250.90
7 purchase totals =	$978.78		$1,064.0592	$1,064.05	$1,064.05	$1,064.00