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	$210.86	13.296%	$238.8959	$238.90	$238.90	$238.90
Purchase #2	$125.28	5.217%	$131.8159	$131.82	$131.80	$131.80
Purchase #3	$91.63	13.582%	$104.0752	$104.08	$104.10	$104.10
Purchase #4	$61.57	5.756%	$65.114	$65.11	$65.10	$65.10
Purchase #5	$174.81	4.424%	$182.5436	$182.54	$182.55	$182.50
Purchase #6	$86.37	13.776%	$98.2683	$98.27	$98.25	$98.30
Purchase #7	$204.83	13.714%	$232.9204	$232.92	$232.90	$232.90
7 purchase totals =	$955.35		$1,053.6333	$1,053.64	$1,053.60	$1,053.60