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	$167.41	5.491%	$176.6025	$176.60	$176.60	$176.60
Purchase #2	$14.91	3.146%	$15.3791	$15.38	$15.40	$15.40
Purchase #3	$216.97	5.587%	$229.0921	$229.09	$229.10	$229.10
Purchase #4	$134.97	11.199%	$150.0853	$150.09	$150.10	$150.10
Purchase #5	$40.55	4.569%	$42.4027	$42.40	$42.40	$42.40
Purchase #6	$238.72	7.223%	$255.9627	$255.96	$255.95	$256.00
Purchase #7	$131.31	7.619%	$141.3145	$141.31	$141.30	$141.30
7 purchase totals =	$944.84		$1,010.8389	$1,010.83	$1,010.85	$1,010.90