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	$97.50	12.183%	$109.3784	$109.38	$109.40	$109.40
Purchase #2	$190.37	11.220%	$211.7295	$211.73	$211.75	$211.70
Purchase #3	$198.58	7.118%	$212.7149	$212.71	$212.70	$212.70
Purchase #4	$213.95	11.679%	$238.9372	$238.94	$238.95	$238.90
Purchase #5	$200.56	6.223%	$213.0408	$213.04	$213.05	$213.00
Purchase #6	$97.94	4.426%	$102.2748	$102.27	$102.25	$102.30
Purchase #7	$77.53	7.405%	$83.2711	$83.27	$83.25	$83.30
7 purchase totals =	$1,076.43		$1,171.3467	$1,171.34	$1,171.35	$1,171.30