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	$203.89	7.849%	$219.8933	$219.89	$219.90	$219.90
Purchase #2	$153.59	4.689%	$160.7918	$160.79	$160.80	$160.80
Purchase #3	$174.93	11.384%	$194.844	$194.84	$194.85	$194.80
Purchase #4	$189.88	11.433%	$211.589	$211.59	$211.60	$211.60
Purchase #5	$70.66	3.262%	$72.9649	$72.96	$72.95	$73.00
Purchase #6	$217.53	13.844%	$247.6449	$247.64	$247.65	$247.60
Purchase #7	$129.85	9.595%	$142.3091	$142.31	$142.30	$142.30
7 purchase totals =	$1,140.33		$1,250.0370	$1,250.02	$1,250.05	$1,250.00