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	$199.50	4.308%	$208.0945	$208.09	$208.10	$208.10
Purchase #2	$66.47	8.591%	$72.1804	$72.18	$72.20	$72.20
Purchase #3	$122.27	12.287%	$137.2933	$137.29	$137.30	$137.30
Purchase #4	$193.69	4.267%	$201.9548	$201.95	$201.95	$202.00
Purchase #5	$44.29	6.449%	$47.1463	$47.15	$47.15	$47.10
Purchase #6	$205.50	4.735%	$215.2304	$215.23	$215.25	$215.20
Purchase #7	$114.56	11.447%	$127.6737	$127.67	$127.65	$127.70
7 purchase totals =	$946.28		$1,009.5734	$1,009.56	$1,009.60	$1,009.60