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	$200.45	9.545%	$219.583	$219.58	$219.60	$219.60
Purchase #2	$249.30	3.689%	$258.4967	$258.50	$258.50	$258.50
Purchase #3	$242.61	5.686%	$256.4048	$256.40	$256.40	$256.40
Purchase #4	$164.62	12.645%	$185.4362	$185.44	$185.45	$185.40
Purchase #5	$240.89	6.402%	$256.3118	$256.31	$256.30	$256.30
Purchase #6	$35.44	7.275%	$38.0183	$38.02	$38.00	$38.00
Purchase #7	$167.65	11.108%	$186.2726	$186.27	$186.25	$186.30
7 purchase totals =	$1,300.96		$1,400.5234	$1,400.52	$1,400.50	$1,400.50