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	$111.34	5.343%	$117.2889	$117.29	$117.30	$117.30
Purchase #2	$62.80	4.322%	$65.5142	$65.51	$65.50	$65.50
Purchase #3	$220.39	6.119%	$233.8757	$233.88	$233.90	$233.90
Purchase #4	$34.92	5.284%	$36.7652	$36.77	$36.75	$36.80
Purchase #5	$86.79	11.291%	$96.5895	$96.59	$96.60	$96.60
Purchase #6	$139.40	11.802%	$155.852	$155.85	$155.85	$155.90
Purchase #7	$60.26	11.393%	$67.1254	$67.13	$67.15	$67.10
7 purchase totals =	$715.90		$773.0109	$773.02	$773.05	$773.10