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	$150.82	4.518%	$157.634	$157.63	$157.65	$157.60
Purchase #2	$40.86	4.321%	$42.6256	$42.63	$42.65	$42.60
Purchase #3	$173.66	13.268%	$196.7012	$196.70	$196.70	$196.70
Purchase #4	$161.93	6.150%	$171.8887	$171.89	$171.90	$171.90
Purchase #5	$38.80	12.439%	$43.6263	$43.63	$43.65	$43.60
Purchase #6	$171.80	8.407%	$186.2432	$186.24	$186.25	$186.20
Purchase #7	$114.47	11.539%	$127.6787	$127.68	$127.70	$127.70
7 purchase totals =	$852.34		$926.3977	$926.40	$926.50	$926.30