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	$200.31	8.517%	$217.3704	$217.37	$217.35	$217.40
Purchase #2	$62.94	4.167%	$65.5627	$65.56	$65.55	$65.60
Purchase #3	$78.89	8.843%	$85.8662	$85.87	$85.85	$85.90
Purchase #4	$158.97	13.263%	$180.0542	$180.05	$180.05	$180.10
Purchase #5	$242.72	3.307%	$250.7468	$250.75	$250.75	$250.70
Purchase #6	$195.33	10.814%	$216.453	$216.45	$216.45	$216.50
Purchase #7	$204.45	9.550%	$223.975	$223.98	$224.00	$224.00
7 purchase totals =	$1,143.61		$1,240.0283	$1,240.03	$1,240.00	$1,240.20