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	$152.93	13.122%	$172.9975	$173.00	$173.00	$173.00
Purchase #2	$39.33	13.807%	$44.7603	$44.76	$44.75	$44.80
Purchase #3	$125.97	12.181%	$141.3144	$141.31	$141.30	$141.30
Purchase #4	$176.46	12.742%	$198.9445	$198.94	$198.95	$198.90
Purchase #5	$198.32	8.682%	$215.5381	$215.54	$215.55	$215.50
Purchase #6	$112.92	12.796%	$127.3692	$127.37	$127.35	$127.40
Purchase #7	$187.63	6.867%	$200.5146	$200.51	$200.50	$200.50
7 purchase totals =	$993.56		$1,101.4386	$1,101.43	$1,101.40	$1,101.40