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	$73.33	6.455%	$78.0635	$78.06	$78.05	$78.10
Purchase #2	$118.85	10.693%	$131.5586	$131.56	$131.55	$131.60
Purchase #3	$73.64	3.338%	$76.0981	$76.10	$76.10	$76.10
Purchase #4	$121.31	4.511%	$126.7823	$126.78	$126.80	$126.80
Purchase #5	$94.32	9.361%	$103.1493	$103.15	$103.15	$103.10
Purchase #6	$160.76	11.694%	$179.5593	$179.56	$179.55	$179.60
Purchase #7	$239.97	6.402%	$255.3329	$255.33	$255.35	$255.30
7 purchase totals =	$882.18		$950.5440	$950.54	$950.55	$950.60