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	$151.81	9.715%	$166.5583	$166.56	$166.55	$166.60
Purchase #2	$132.53	7.561%	$142.5506	$142.55	$142.55	$142.60
Purchase #3	$7.46	8.407%	$8.0872	$8.09	$8.10	$8.10
Purchase #4	$220.89	10.296%	$243.6328	$243.63	$243.65	$243.60
Purchase #5	$86.25	4.170%	$89.8466	$89.85	$89.85	$89.80
Purchase #6	$73.70	9.413%	$80.6374	$80.64	$80.65	$80.60
Purchase #7	$148.64	13.646%	$168.9234	$168.92	$168.90	$168.90
7 purchase totals =	$821.28		$900.2363	$900.24	$900.25	$900.20