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	$135.55	4.734%	$141.9669	$141.97	$141.95	$142.00
Purchase #2	$56.89	13.511%	$64.5764	$64.58	$64.60	$64.60
Purchase #3	$9.83	12.785%	$11.0868	$11.09	$11.10	$11.10
Purchase #4	$30.37	4.610%	$31.7701	$31.77	$31.75	$31.80
Purchase #5	$172.47	7.280%	$185.0258	$185.03	$185.05	$185.00
Purchase #6	$93.64	8.839%	$101.9168	$101.92	$101.90	$101.90
Purchase #7	$224.35	13.800%	$255.3103	$255.31	$255.30	$255.30
7 purchase totals =	$723.10		$791.6531	$791.67	$791.65	$791.70