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	$224.86	10.711%	$248.9448	$248.94	$248.95	$248.90
Purchase #2	$97.76	13.702%	$111.1551	$111.16	$111.15	$111.20
Purchase #3	$230.69	3.458%	$238.6673	$238.67	$238.65	$238.70
Purchase #4	$72.79	12.386%	$81.8058	$81.81	$81.80	$81.80
Purchase #5	$226.77	7.210%	$243.1201	$243.12	$243.10	$243.10
Purchase #6	$71.34	4.510%	$74.5574	$74.56	$74.55	$74.60
Purchase #7	$45.78	13.861%	$52.1256	$52.13	$52.15	$52.10
7 purchase totals =	$969.99		$1,050.3761	$1,050.39	$1,050.35	$1,050.40