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	$235.92	3.586%	$244.3801	$244.38	$244.40	$244.40
Purchase #2	$247.39	3.745%	$256.6548	$256.65	$256.65	$256.70
Purchase #3	$44.29	12.579%	$49.8612	$49.86	$49.85	$49.90
Purchase #4	$118.33	4.354%	$123.4821	$123.48	$123.50	$123.50
Purchase #5	$114.61	8.407%	$124.2453	$124.25	$124.25	$124.20
Purchase #6	$157.81	13.357%	$178.8887	$178.89	$178.90	$178.90
Purchase #7	$101.25	12.579%	$113.9862	$113.99	$114.00	$114.00
7 purchase totals =	$1,019.60		$1,091.4984	$1,091.50	$1,091.55	$1,091.60