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	$69.26	12.563%	$77.9611	$77.96	$77.95	$78.00
Purchase #2	$98.77	11.321%	$109.9518	$109.95	$109.95	$110.00
Purchase #3	$78.41	4.636%	$82.0451	$82.05	$82.05	$82.00
Purchase #4	$131.84	8.478%	$143.0174	$143.02	$143.00	$143.00
Purchase #5	$196.98	9.421%	$215.5375	$215.54	$215.55	$215.50
Purchase #6	$78.53	6.311%	$83.486	$83.49	$83.50	$83.50
Purchase #7	$21.78	7.587%	$23.4324	$23.43	$23.45	$23.40
7 purchase totals =	$675.57		$735.4313	$735.44	$735.45	$735.40