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	$118.76	5.236%	$124.9783	$124.98	$125.00	$125.00
Purchase #2	$126.99	3.641%	$131.6137	$131.61	$131.60	$131.60
Purchase #3	$64.25	13.532%	$72.9443	$72.94	$72.95	$72.90
Purchase #4	$39.95	5.871%	$42.2955	$42.30	$42.30	$42.30
Purchase #5	$151.55	4.497%	$158.3652	$158.37	$158.35	$158.40
Purchase #6	$28.87	10.847%	$32.0015	$32.00	$32.00	$32.00
Purchase #7	$232.32	6.775%	$248.0597	$248.06	$248.05	$248.10
7 purchase totals =	$762.69		$810.2582	$810.26	$810.25	$810.30