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	$82.60	11.405%	$92.0205	$92.02	$92.00	$92.00
Purchase #2	$123.51	6.564%	$131.6172	$131.62	$131.60	$131.60
Purchase #3	$127.39	3.588%	$131.9608	$131.96	$131.95	$132.00
Purchase #4	$49.71	5.321%	$52.3551	$52.36	$52.35	$52.40
Purchase #5	$131.62	6.860%	$140.6491	$140.65	$140.65	$140.60
Purchase #6	$79.45	5.315%	$83.6728	$83.67	$83.65	$83.70
Purchase #7	$135.71	12.535%	$152.7212	$152.72	$152.70	$152.70
7 purchase totals =	$729.99		$784.9967	$785.00	$784.90	$785.00