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	$236.83	5.759%	$250.469	$250.47	$250.45	$250.50
Purchase #2	$85.53	6.196%	$90.8294	$90.83	$90.85	$90.80
Purchase #3	$138.29	3.526%	$143.1661	$143.17	$143.15	$143.20
Purchase #4	$119.67	11.255%	$133.1389	$133.14	$133.15	$133.10
Purchase #5	$141.69	5.263%	$149.1471	$149.15	$149.15	$149.10
Purchase #6	$226.71	9.804%	$248.9366	$248.94	$248.95	$248.90
Purchase #7	$62.27	5.702%	$65.8206	$65.82	$65.80	$65.80
7 purchase totals =	$1,010.99		$1,081.5077	$1,081.52	$1,081.50	$1,081.40