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	$109.34	4.222%	$113.9563	$113.96	$113.95	$114.00
Purchase #2	$184.37	4.859%	$193.3285	$193.33	$193.35	$193.30
Purchase #3	$35.79	7.808%	$38.5845	$38.58	$38.60	$38.60
Purchase #4	$42.74	7.550%	$45.9669	$45.97	$45.95	$46.00
Purchase #5	$99.69	11.358%	$111.0128	$111.01	$111.00	$111.00
Purchase #6	$186.77	12.606%	$210.3142	$210.31	$210.30	$210.30
Purchase #7	$130.86	12.341%	$147.0094	$147.01	$147.00	$147.00
7 purchase totals =	$789.56		$860.1726	$860.17	$860.15	$860.20