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	$38.67	6.624%	$41.2315	$41.23	$41.25	$41.20
Purchase #2	$226.42	12.834%	$255.4787	$255.48	$255.50	$255.50
Purchase #3	$142.67	6.693%	$152.2189	$152.22	$152.20	$152.20
Purchase #4	$23.44	13.667%	$26.6435	$26.64	$26.65	$26.60
Purchase #5	$165.75	4.429%	$173.0911	$173.09	$173.10	$173.10
Purchase #6	$185.75	5.459%	$195.8901	$195.89	$195.90	$195.90
Purchase #7	$102.55	7.187%	$109.9203	$109.92	$109.90	$109.90
7 purchase totals =	$885.25		$954.4741	$954.47	$954.50	$954.40