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	$89.86	3.284%	$92.811	$92.81	$92.80	$92.80
Purchase #2	$132.94	13.838%	$151.3362	$151.34	$151.35	$151.30
Purchase #3	$5.67	11.282%	$6.3097	$6.31	$6.30	$6.30
Purchase #4	$209.44	5.309%	$220.5592	$220.56	$220.55	$220.60
Purchase #5	$241.91	9.790%	$265.593	$265.59	$265.60	$265.60
Purchase #6	$38.78	13.551%	$44.0351	$44.04	$44.05	$44.00
Purchase #7	$223.36	6.691%	$238.305	$238.31	$238.30	$238.30
7 purchase totals =	$941.96		$1,018.9492	$1,018.96	$1,018.95	$1,018.90