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	$244.88	10.743%	$271.1875	$271.19	$271.20	$271.20
Purchase #2	$89.52	7.464%	$96.2018	$96.20	$96.20	$96.20
Purchase #3	$76.27	8.127%	$82.4685	$82.47	$82.45	$82.50
Purchase #4	$114.25	13.797%	$130.0131	$130.01	$130.00	$130.00
Purchase #5	$62.80	3.328%	$64.89	$64.89	$64.90	$64.90
Purchase #6	$47.43	6.334%	$50.4342	$50.43	$50.45	$50.40
Purchase #7	$32.72	11.219%	$36.3909	$36.39	$36.40	$36.40
7 purchase totals =	$667.87		$731.5860	$731.58	$731.60	$731.60