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	$77.29	12.724%	$87.1244	$87.12	$87.10	$87.10
Purchase #2	$52.48	11.364%	$58.4438	$58.44	$58.45	$58.40
Purchase #3	$198.29	3.802%	$205.829	$205.83	$205.85	$205.80
Purchase #4	$151.61	8.712%	$164.8183	$164.82	$164.80	$164.80
Purchase #5	$209.81	4.338%	$218.9116	$218.91	$218.90	$218.90
Purchase #6	$92.79	6.667%	$98.9763	$98.98	$99.00	$99.00
Purchase #7	$223.86	3.426%	$231.5294	$231.53	$231.55	$231.50
7 purchase totals =	$1,006.13		$1,065.6328	$1,065.63	$1,065.65	$1,065.50