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	$58.67	4.553%	$61.3412	$61.34	$61.35	$61.30
Purchase #2	$232.87	4.691%	$243.7939	$243.79	$243.80	$243.80
Purchase #3	$139.43	8.332%	$151.0473	$151.05	$151.05	$151.00
Purchase #4	$80.82	10.217%	$89.0774	$89.08	$89.10	$89.10
Purchase #5	$205.50	13.871%	$234.0049	$234.00	$234.00	$234.00
Purchase #6	$99.57	9.755%	$109.2831	$109.28	$109.30	$109.30
Purchase #7	$135.44	3.238%	$139.8255	$139.83	$139.85	$139.80
7 purchase totals =	$952.30		$1,028.3733	$1,028.37	$1,028.45	$1,028.30