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	$72.73	3.563%	$75.3214	$75.32	$75.30	$75.30
Purchase #2	$117.67	6.623%	$125.4633	$125.46	$125.45	$125.50
Purchase #3	$88.72	7.648%	$95.5053	$95.51	$95.50	$95.50
Purchase #4	$231.29	4.323%	$241.2887	$241.29	$241.30	$241.30
Purchase #5	$124.80	13.399%	$141.522	$141.52	$141.50	$141.50
Purchase #6	$29.81	7.535%	$32.0562	$32.06	$32.05	$32.10
Purchase #7	$68.47	6.337%	$72.8089	$72.81	$72.80	$72.80
7 purchase totals =	$733.49		$783.9658	$783.97	$783.90	$784.00