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	$81.58	10.478%	$90.128	$90.13	$90.15	$90.10
Purchase #2	$107.38	12.377%	$120.6704	$120.67	$120.65	$120.70
Purchase #3	$96.80	7.501%	$104.061	$104.06	$104.05	$104.10
Purchase #4	$54.81	3.339%	$56.6401	$56.64	$56.65	$56.60
Purchase #5	$168.85	12.437%	$189.8499	$189.85	$189.85	$189.80
Purchase #6	$11.47	11.262%	$12.7618	$12.76	$12.75	$12.80
Purchase #7	$144.64	11.581%	$161.3908	$161.39	$161.40	$161.40
7 purchase totals =	$665.53		$735.5020	$735.50	$735.50	$735.50