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	$198.45	11.181%	$220.6387	$220.64	$220.65	$220.60
Purchase #2	$82.31	10.264%	$90.7583	$90.76	$90.75	$90.80
Purchase #3	$127.61	12.849%	$144.0066	$144.01	$144.00	$144.00
Purchase #4	$42.59	5.388%	$44.8847	$44.88	$44.90	$44.90
Purchase #5	$146.75	10.539%	$162.216	$162.22	$162.20	$162.20
Purchase #6	$238.77	7.416%	$256.4772	$256.48	$256.50	$256.50
Purchase #7	$229.67	3.126%	$236.8495	$236.85	$236.85	$236.80
7 purchase totals =	$1,066.15		$1,155.8310	$1,155.84	$1,155.85	$1,155.80