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	$243.41	7.544%	$261.7729	$261.77	$261.75	$261.80
Purchase #2	$111.40	11.137%	$123.8066	$123.81	$123.80	$123.80
Purchase #3	$192.88	8.688%	$209.6374	$209.64	$209.65	$209.60
Purchase #4	$104.51	13.833%	$118.9669	$118.97	$118.95	$119.00
Purchase #5	$38.73	11.512%	$43.1886	$43.19	$43.20	$43.20
Purchase #6	$111.54	6.845%	$119.1749	$119.17	$119.15	$119.20
Purchase #7	$127.35	6.811%	$136.0238	$136.02	$136.00	$136.00
7 purchase totals =	$929.82		$1,012.5711	$1,012.57	$1,012.50	$1,012.60