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	$240.89	9.106%	$262.8254	$262.83	$262.85	$262.80
Purchase #2	$17.61	12.654%	$19.8384	$19.84	$19.85	$19.80
Purchase #3	$111.65	10.612%	$123.4983	$123.50	$123.50	$123.50
Purchase #4	$157.37	6.408%	$167.4543	$167.45	$167.45	$167.50
Purchase #5	$49.36	6.144%	$52.3927	$52.39	$52.40	$52.40
Purchase #6	$110.74	6.306%	$117.7233	$117.72	$117.70	$117.70
Purchase #7	$242.38	7.108%	$259.6084	$259.61	$259.60	$259.60
7 purchase totals =	$930.00		$1,003.3408	$1,003.34	$1,003.35	$1,003.30