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	$180.89	9.718%	$198.4689	$198.47	$198.45	$198.50
Purchase #2	$14.36	5.807%	$15.1939	$15.19	$15.20	$15.20
Purchase #3	$64.87	12.362%	$72.8892	$72.89	$72.90	$72.90
Purchase #4	$18.84	12.190%	$21.1366	$21.14	$21.15	$21.10
Purchase #5	$213.83	3.150%	$220.5656	$220.57	$220.55	$220.60
Purchase #6	$53.89	4.641%	$56.391	$56.39	$56.40	$56.40
Purchase #7	$154.49	3.760%	$160.2988	$160.30	$160.30	$160.30
7 purchase totals =	$701.17		$744.9440	$744.95	$744.95	$745.00