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	$76.71	5.499%	$80.9283	$80.93	$80.95	$80.90
Purchase #2	$211.45	9.112%	$230.7173	$230.72	$230.70	$230.70
Purchase #3	$45.34	12.658%	$51.0791	$51.08	$51.10	$51.10
Purchase #4	$145.32	11.444%	$161.9504	$161.95	$161.95	$162.00
Purchase #5	$223.58	6.691%	$238.5397	$238.54	$238.55	$238.50
Purchase #6	$200.89	4.224%	$209.3756	$209.38	$209.40	$209.40
Purchase #7	$243.89	4.702%	$255.3577	$255.36	$255.35	$255.40
7 purchase totals =	$1,147.18		$1,227.9481	$1,227.96	$1,228.00	$1,228.00