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	$43.44	9.664%	$47.638	$47.64	$47.65	$47.60
Purchase #2	$30.35	7.387%	$32.592	$32.59	$32.60	$32.60
Purchase #3	$244.97	11.796%	$273.8667	$273.87	$273.85	$273.90
Purchase #4	$83.92	7.139%	$89.911	$89.91	$89.90	$89.90
Purchase #5	$101.49	9.577%	$111.2097	$111.21	$111.20	$111.20
Purchase #6	$33.36	8.452%	$36.1796	$36.18	$36.20	$36.20
Purchase #7	$35.78	8.565%	$38.8446	$38.84	$38.85	$38.80
7 purchase totals =	$573.31		$630.2416	$630.24	$630.25	$630.20