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	$94.90	13.686%	$107.888	$107.89	$107.90	$107.90
Purchase #2	$146.81	13.288%	$166.3181	$166.32	$166.30	$166.30
Purchase #3	$243.27	6.624%	$259.3842	$259.38	$259.40	$259.40
Purchase #4	$145.29	7.608%	$156.3437	$156.34	$156.35	$156.30
Purchase #5	$134.67	6.381%	$143.2633	$143.26	$143.25	$143.30
Purchase #6	$137.64	10.516%	$152.1142	$152.11	$152.10	$152.10
Purchase #7	$202.59	9.345%	$221.522	$221.52	$221.50	$221.50
7 purchase totals =	$1,105.17		$1,206.8335	$1,206.82	$1,206.80	$1,206.80