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	$63.83	7.760%	$68.7832	$68.78	$68.80	$68.80
Purchase #2	$70.49	11.652%	$78.7035	$78.70	$78.70	$78.70
Purchase #3	$196.89	3.769%	$204.3108	$204.31	$204.30	$204.30
Purchase #4	$77.72	4.601%	$81.2959	$81.30	$81.30	$81.30
Purchase #5	$74.43	6.104%	$78.9732	$78.97	$78.95	$79.00
Purchase #6	$108.28	9.788%	$118.8784	$118.88	$118.90	$118.90
Purchase #7	$82.79	3.675%	$85.8325	$85.83	$85.85	$85.80
7 purchase totals =	$674.43		$716.7775	$716.77	$716.80	$716.80