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	$206.63	4.332%	$215.5812	$215.58	$215.60	$215.60
Purchase #2	$148.76	10.787%	$164.8067	$164.81	$164.80	$164.80
Purchase #3	$84.41	6.619%	$89.9971	$90.00	$90.00	$90.00
Purchase #4	$220.27	11.189%	$244.916	$244.92	$244.90	$244.90
Purchase #5	$114.40	4.336%	$119.3604	$119.36	$119.35	$119.40
Purchase #6	$179.46	11.862%	$200.7475	$200.75	$200.75	$200.70
Purchase #7	$9.69	9.137%	$10.5754	$10.58	$10.60	$10.60
7 purchase totals =	$963.62		$1,045.9843	$1,046.00	$1,046.00	$1,046.00