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	$36.46	9.278%	$39.8428	$39.84	$39.85	$39.80
Purchase #2	$118.90	7.138%	$127.3871	$127.39	$127.40	$127.40
Purchase #3	$237.71	7.120%	$254.635	$254.64	$254.65	$254.60
Purchase #4	$213.44	11.548%	$238.0881	$238.09	$238.10	$238.10
Purchase #5	$222.67	5.773%	$235.5247	$235.52	$235.50	$235.50
Purchase #6	$36.31	11.589%	$40.518	$40.52	$40.50	$40.50
Purchase #7	$245.56	4.201%	$255.876	$255.88	$255.90	$255.90
7 purchase totals =	$1,111.05		$1,191.8717	$1,191.88	$1,191.90	$1,191.80