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	$89.34	5.443%	$94.2028	$94.20	$94.20	$94.20
Purchase #2	$147.88	11.507%	$164.8966	$164.90	$164.90	$164.90
Purchase #3	$95.36	5.214%	$100.3321	$100.33	$100.35	$100.30
Purchase #4	$138.40	13.193%	$156.6591	$156.66	$156.65	$156.70
Purchase #5	$126.72	3.848%	$131.5962	$131.60	$131.60	$131.60
Purchase #6	$50.85	8.855%	$55.3528	$55.35	$55.35	$55.40
Purchase #7	$5.40	6.805%	$5.7675	$5.77	$5.75	$5.80
7 purchase totals =	$653.95		$708.8071	$708.81	$708.80	$708.90