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	$115.46	10.276%	$127.3247	$127.32	$127.30	$127.30
Purchase #2	$230.82	4.371%	$240.9091	$240.91	$240.90	$240.90
Purchase #3	$25.47	13.211%	$28.8348	$28.83	$28.85	$28.80
Purchase #4	$249.63	4.835%	$261.6996	$261.70	$261.70	$261.70
Purchase #5	$109.31	11.530%	$121.9134	$121.91	$121.90	$121.90
Purchase #6	$187.27	11.724%	$209.2255	$209.23	$209.25	$209.20
Purchase #7	$144.67	11.370%	$161.119	$161.12	$161.10	$161.10
7 purchase totals =	$1,062.63		$1,151.0261	$1,151.02	$1,151.00	$1,150.90