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	$229.32	10.835%	$254.1668	$254.17	$254.15	$254.20
Purchase #2	$50.28	10.548%	$55.5835	$55.58	$55.60	$55.60
Purchase #3	$133.73	5.672%	$141.3152	$141.32	$141.30	$141.30
Purchase #4	$233.93	6.115%	$248.2348	$248.23	$248.25	$248.20
Purchase #5	$220.29	4.513%	$230.2317	$230.23	$230.25	$230.20
Purchase #6	$139.52	7.525%	$150.0189	$150.02	$150.00	$150.00
Purchase #7	$47.47	9.630%	$52.0414	$52.04	$52.05	$52.00
7 purchase totals =	$1,054.54		$1,131.5923	$1,131.59	$1,131.60	$1,131.50