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	$136.44	4.527%	$142.6166	$142.62	$142.60	$142.60
Purchase #2	$241.90	5.252%	$254.6046	$254.60	$254.60	$254.60
Purchase #3	$43.44	11.108%	$48.2653	$48.27	$48.25	$48.30
Purchase #4	$54.76	5.643%	$57.8501	$57.85	$57.85	$57.90
Purchase #5	$110.95	11.330%	$123.5206	$123.52	$123.50	$123.50
Purchase #6	$209.35	5.463%	$220.7868	$220.79	$220.80	$220.80
Purchase #7	$184.45	4.424%	$192.6101	$192.61	$192.60	$192.60
7 purchase totals =	$981.29		$1,040.2541	$1,040.26	$1,040.20	$1,040.30