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	$119.71	6.166%	$127.0913	$127.09	$127.10	$127.10
Purchase #2	$234.27	11.663%	$261.5929	$261.59	$261.60	$261.60
Purchase #3	$32.29	6.605%	$34.4228	$34.42	$34.40	$34.40
Purchase #4	$37.90	13.799%	$43.1298	$43.13	$43.15	$43.10
Purchase #5	$182.59	12.790%	$205.9433	$205.94	$205.95	$205.90
Purchase #6	$126.35	3.773%	$131.1172	$131.12	$131.10	$131.10
Purchase #7	$188.37	9.830%	$206.8868	$206.89	$206.90	$206.90
7 purchase totals =	$921.48		$1,010.1841	$1,010.18	$1,010.20	$1,010.10