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	$54.49	12.757%	$61.4413	$61.44	$61.45	$61.40
Purchase #2	$226.83	3.352%	$234.4333	$234.43	$234.45	$234.40
Purchase #3	$80.30	6.225%	$85.2987	$85.30	$85.30	$85.30
Purchase #4	$35.51	7.110%	$38.0348	$38.03	$38.05	$38.00
Purchase #5	$77.54	11.570%	$86.5114	$86.51	$86.50	$86.50
Purchase #6	$238.39	9.505%	$261.049	$261.05	$261.05	$261.00
Purchase #7	$241.44	9.412%	$264.1643	$264.16	$264.15	$264.20
7 purchase totals =	$954.50		$1,030.9328	$1,030.92	$1,030.95	$1,030.80