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	$137.28	13.620%	$155.9775	$155.98	$156.00	$156.00
Purchase #2	$116.98	12.478%	$131.5768	$131.58	$131.60	$131.60
Purchase #3	$104.73	4.710%	$109.6628	$109.66	$109.65	$109.70
Purchase #4	$236.63	9.405%	$258.8851	$258.89	$258.90	$258.90
Purchase #5	$163.90	3.603%	$169.8053	$169.81	$169.80	$169.80
Purchase #6	$65.67	6.267%	$69.7855	$69.79	$69.80	$69.80
Purchase #7	$35.96	5.139%	$37.808	$37.81	$37.80	$37.80
7 purchase totals =	$861.15		$933.5010	$933.52	$933.55	$933.60