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	$101.41	7.424%	$108.9387	$108.94	$108.95	$108.90
Purchase #2	$212.37	5.114%	$223.2306	$223.23	$223.25	$223.20
Purchase #3	$76.32	8.686%	$82.9492	$82.95	$82.95	$82.90
Purchase #4	$181.98	12.783%	$205.2425	$205.24	$205.25	$205.20
Purchase #5	$92.55	13.395%	$104.9471	$104.95	$104.95	$104.90
Purchase #6	$136.31	13.381%	$154.5496	$154.55	$154.55	$154.50
Purchase #7	$38.58	5.240%	$40.6016	$40.60	$40.60	$40.60
7 purchase totals =	$839.52		$920.4593	$920.46	$920.50	$920.20