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	$183.82	11.715%	$205.3545	$205.35	$205.35	$205.40
Purchase #2	$191.44	10.466%	$211.4761	$211.48	$211.50	$211.50
Purchase #3	$139.63	9.227%	$152.5137	$152.51	$152.50	$152.50
Purchase #4	$64.35	11.594%	$71.8107	$71.81	$71.80	$71.80
Purchase #5	$172.69	13.520%	$196.0377	$196.04	$196.05	$196.00
Purchase #6	$83.25	3.285%	$85.9848	$85.98	$86.00	$86.00
Purchase #7	$139.97	9.329%	$153.0278	$153.03	$153.05	$153.00
7 purchase totals =	$975.15		$1,076.2053	$1,076.20	$1,076.25	$1,076.20