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	$187.73	6.525%	$199.9794	$199.98	$200.00	$200.00
Purchase #2	$56.97	9.645%	$62.4648	$62.46	$62.45	$62.50
Purchase #3	$33.61	12.507%	$37.8136	$37.81	$37.80	$37.80
Purchase #4	$40.83	12.143%	$45.788	$45.79	$45.80	$45.80
Purchase #5	$238.58	6.546%	$254.1974	$254.20	$254.20	$254.20
Purchase #6	$136.77	11.136%	$152.0007	$152.00	$152.00	$152.00
Purchase #7	$233.92	6.557%	$249.2581	$249.26	$249.25	$249.30
7 purchase totals =	$928.41		$1,001.5020	$1,001.50	$1,001.50	$1,001.60