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	$192.80	9.235%	$210.6051	$210.61	$210.60	$210.60
Purchase #2	$90.41	12.300%	$101.5304	$101.53	$101.55	$101.50
Purchase #3	$101.57	12.457%	$114.2226	$114.22	$114.20	$114.20
Purchase #4	$57.54	8.539%	$62.4533	$62.45	$62.45	$62.50
Purchase #5	$60.60	8.407%	$65.6946	$65.69	$65.70	$65.70
Purchase #6	$95.80	13.735%	$108.9581	$108.96	$108.95	$109.00
Purchase #7	$118.79	7.691%	$127.9261	$127.93	$127.95	$127.90
7 purchase totals =	$717.51		$791.3902	$791.39	$791.40	$791.40