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	$181.57	6.415%	$193.2177	$193.22	$193.20	$193.20
Purchase #2	$215.31	3.111%	$222.0083	$222.01	$222.00	$222.00
Purchase #3	$64.87	3.845%	$67.3643	$67.36	$67.35	$67.40
Purchase #4	$54.88	5.287%	$57.7815	$57.78	$57.80	$57.80
Purchase #5	$188.47	6.244%	$200.2381	$200.24	$200.25	$200.20
Purchase #6	$232.62	9.248%	$254.1327	$254.13	$254.15	$254.10
Purchase #7	$83.88	8.284%	$90.8286	$90.83	$90.85	$90.80
7 purchase totals =	$1,021.60		$1,085.5712	$1,085.57	$1,085.60	$1,085.50