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	$81.46	7.387%	$87.4775	$87.48	$87.50	$87.50
Purchase #2	$47.65	11.785%	$53.2656	$53.27	$53.25	$53.30
Purchase #3	$89.95	11.748%	$100.5173	$100.52	$100.50	$100.50
Purchase #4	$180.36	13.153%	$204.0828	$204.08	$204.10	$204.10
Purchase #5	$214.64	3.730%	$222.6461	$222.65	$222.65	$222.60
Purchase #6	$103.65	8.623%	$112.5877	$112.59	$112.60	$112.60
Purchase #7	$10.90	7.502%	$11.7177	$11.72	$11.70	$11.70
7 purchase totals =	$728.61		$792.2947	$792.31	$792.30	$792.30