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	$50.88	13.719%	$57.8602	$57.86	$57.85	$57.90
Purchase #2	$194.73	11.601%	$217.3206	$217.32	$217.30	$217.30
Purchase #3	$114.83	8.749%	$124.8765	$124.88	$124.90	$124.90
Purchase #4	$184.44	4.183%	$192.1551	$192.16	$192.15	$192.20
Purchase #5	$239.79	10.264%	$264.402	$264.40	$264.40	$264.40
Purchase #6	$113.36	12.524%	$127.5572	$127.56	$127.55	$127.60
Purchase #7	$36.64	3.408%	$37.8887	$37.89	$37.90	$37.90
7 purchase totals =	$934.67		$1,022.0603	$1,022.07	$1,022.05	$1,022.20