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	$237.48	10.119%	$261.5106	$261.51	$261.50	$261.50
Purchase #2	$61.25	9.578%	$67.1165	$67.12	$67.10	$67.10
Purchase #3	$195.83	6.680%	$208.9114	$208.91	$208.90	$208.90
Purchase #4	$26.41	4.849%	$27.6906	$27.69	$27.70	$27.70
Purchase #5	$116.56	7.376%	$125.1575	$125.16	$125.15	$125.20
Purchase #6	$34.40	10.141%	$37.8885	$37.89	$37.90	$37.90
Purchase #7	$249.92	13.599%	$283.9066	$283.91	$283.90	$283.90
7 purchase totals =	$921.85		$1,012.1817	$1,012.19	$1,012.15	$1,012.20