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	$78.36	9.272%	$85.6255	$85.63	$85.65	$85.60
Purchase #2	$33.64	4.748%	$35.2372	$35.24	$35.25	$35.20
Purchase #3	$125.80	11.382%	$140.1186	$140.12	$140.10	$140.10
Purchase #4	$93.43	9.491%	$102.2974	$102.30	$102.30	$102.30
Purchase #5	$94.95	7.320%	$101.9003	$101.90	$101.90	$101.90
Purchase #6	$108.44	9.123%	$118.333	$118.33	$118.35	$118.30
Purchase #7	$82.62	8.224%	$89.4147	$89.41	$89.40	$89.40
7 purchase totals =	$617.24		$672.9267	$672.93	$672.95	$672.80