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	$203.52	10.215%	$224.3096	$224.31	$224.30	$224.30
Purchase #2	$105.93	5.600%	$111.8621	$111.86	$111.85	$111.90
Purchase #3	$208.27	13.520%	$236.4281	$236.43	$236.45	$236.40
Purchase #4	$238.70	3.578%	$247.2407	$247.24	$247.25	$247.20
Purchase #5	$221.89	7.274%	$238.0303	$238.03	$238.05	$238.00
Purchase #6	$243.52	9.351%	$266.2916	$266.29	$266.30	$266.30
Purchase #7	$168.39	3.341%	$174.0159	$174.02	$174.00	$174.00
7 purchase totals =	$1,390.22		$1,498.1783	$1,498.18	$1,498.20	$1,498.10