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	$77.82	11.626%	$86.8674	$86.87	$86.85	$86.90
Purchase #2	$116.38	6.122%	$123.5048	$123.50	$123.50	$123.50
Purchase #3	$232.75	4.797%	$243.915	$243.92	$243.90	$243.90
Purchase #4	$112.69	10.561%	$124.5912	$124.59	$124.60	$124.60
Purchase #5	$60.56	4.645%	$63.373	$63.37	$63.35	$63.40
Purchase #6	$174.94	7.727%	$188.4576	$188.46	$188.45	$188.50
Purchase #7	$6.92	4.185%	$7.2096	$7.21	$7.20	$7.20
7 purchase totals =	$782.06		$837.9186	$837.92	$837.85	$838.00