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	$58.34	7.792%	$62.8859	$62.89	$62.90	$62.90
Purchase #2	$151.60	11.383%	$168.8566	$168.86	$168.85	$168.90
Purchase #3	$36.50	11.245%	$40.6044	$40.60	$40.60	$40.60
Purchase #4	$106.86	3.122%	$110.1962	$110.20	$110.20	$110.20
Purchase #5	$227.62	3.510%	$235.6095	$235.61	$235.60	$235.60
Purchase #6	$170.83	7.118%	$182.9897	$182.99	$183.00	$183.00
Purchase #7	$225.47	12.831%	$254.4001	$254.40	$254.40	$254.40
7 purchase totals =	$977.22		$1,055.5424	$1,055.55	$1,055.55	$1,055.60