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	$71.96	7.425%	$77.303	$77.30	$77.30	$77.30
Purchase #2	$68.44	8.557%	$74.2964	$74.30	$74.30	$74.30
Purchase #3	$178.37	5.442%	$188.0769	$188.08	$188.10	$188.10
Purchase #4	$236.57	8.384%	$256.404	$256.40	$256.40	$256.40
Purchase #5	$82.85	3.217%	$85.5153	$85.52	$85.50	$85.50
Purchase #6	$73.55	10.472%	$81.2522	$81.25	$81.25	$81.30
Purchase #7	$231.49	4.109%	$241.0019	$241.00	$241.00	$241.00
7 purchase totals =	$943.23		$1,003.8497	$1,003.85	$1,003.85	$1,003.90