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	$91.80	10.674%	$101.5987	$101.60	$101.60	$101.60
Purchase #2	$38.95	10.655%	$43.1001	$43.10	$43.10	$43.10
Purchase #3	$233.65	13.804%	$265.903	$265.90	$265.90	$265.90
Purchase #4	$153.92	8.680%	$167.2803	$167.28	$167.30	$167.30
Purchase #5	$145.64	10.236%	$160.5477	$160.55	$160.55	$160.50
Purchase #6	$156.38	4.159%	$162.8838	$162.88	$162.90	$162.90
Purchase #7	$48.93	10.854%	$54.2409	$54.24	$54.25	$54.20
7 purchase totals =	$869.27		$955.5545	$955.55	$955.60	$955.50