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	$117.84	12.405%	$132.4581	$132.46	$132.45	$132.50
Purchase #2	$98.96	13.408%	$112.2286	$112.23	$112.25	$112.20
Purchase #3	$110.79	6.406%	$117.8872	$117.89	$117.90	$117.90
Purchase #4	$29.95	6.484%	$31.892	$31.89	$31.90	$31.90
Purchase #5	$34.67	3.473%	$35.8741	$35.87	$35.85	$35.90
Purchase #6	$162.47	7.179%	$174.1337	$174.13	$174.15	$174.10
Purchase #7	$90.86	10.190%	$100.1186	$100.12	$100.10	$100.10
7 purchase totals =	$645.54		$704.5923	$704.59	$704.60	$704.60