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	$133.91	8.867%	$145.7838	$145.78	$145.80	$145.80
Purchase #2	$238.97	8.714%	$259.7938	$259.79	$259.80	$259.80
Purchase #3	$143.41	5.740%	$151.6417	$151.64	$151.65	$151.60
Purchase #4	$95.38	7.538%	$102.5697	$102.57	$102.55	$102.60
Purchase #5	$121.57	6.341%	$129.2788	$129.28	$129.30	$129.30
Purchase #6	$169.51	9.693%	$185.9406	$185.94	$185.95	$185.90
Purchase #7	$25.88	6.405%	$27.5376	$27.54	$27.55	$27.50
7 purchase totals =	$928.63		$1,002.5460	$1,002.54	$1,002.60	$1,002.50